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Android Studio - How to use implement swipe gesture in android game

I was working on a game on Android studio where user touch drives tiles to combine. To do this, I have used a GridLayout separated into rows and columns. The value is displayed with imageview and all gridlayout cells are linked to a separate cell class which includes imageview ID's. I implemented a listener on each image view to detect when a swiping motion occured. The code for initalizing the board and listeners is below:
for(int i = 0; i<noOfBlocks; i++) {
for (int j = 0; j < noOfBlocks; j++) {
ImageView imageView = new ImageView(this);
imageView.setId(iDcnt);
imageView.setLayoutParams(new ViewGroup.LayoutParams(widthOfBlock, widthOfBlock));
imageView.setMaxHeight(widthOfBlock);
imageView.setMaxWidth(widthOfBlock);
int randomNum = (int) Math.floor(random.nextDouble() * gamepiece.length);
imageView.setImageResource(gamepiece[randomNum]);
Cell c = new Cell(i + 1, j+1, randomNum, imageView.getId());
imageView.setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
SquarePlay s = null;
try {
s = new SquarePlay();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
s.onSwipeEvent(event);
return false;
}
});
gameBoard.addView(imageView);
iDcnt++;
}
The OnTouch events are handled in a separate class in the method which is shown below:
float x1, x2, y1, y2, dx, dy;
public void onSwipeEvent(MotionEvent event){
switch(event.getAction()) {
case(MotionEvent.ACTION_DOWN):
x1 = event.getX();
y1 = event.getY();
break;
case(MotionEvent.ACTION_UP): {
x2 = event.getX();
y2 = event.getY();
dx = x2-x1;
dy = y2-y1;
if(Math.abs(dx) > Math.abs(dy)) {
if(dx>0)
onSwipeRight();
else
onSwipeLeft();
} else {
if(dy>0)
onSwipeDown();
else
onSwipeUp();
}
}
}
}
private void onSwipeLeft() {
System.exit(0);
}
private void onSwipeRight() {
System.exit(0);
}
private void onSwipeUp() {
System.exit(0);
}
private void onSwipeDown() {
System.exit(0);
}
NOTE:System.exit is just there to test if this works.
The App loads but does not produce a response from the swipe events, Does anyone have any suggestions on how to resolve this issue?
Thank you :)

To use swipe You can create your class inside the activity class as follow##
declare the class name inside the activity class
SwipeListener swipeListener;
inside the activity class write this code to handle the swipe##
private class SwipeListener implements View.OnTouchListener {
//create gesture detector variable
GestureDetector gestureDetector;
//create constructor
SwipeListener(View view){
int threshold = 100;
int velocity_threshold = 100;
GestureDetector.SimpleOnGestureListener listener =
new GestureDetector.SimpleOnGestureListener(){
#Override
public boolean onDown(MotionEvent e) {
return super.onDown(e);
}
#Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
//get x and y difference
float xDiff = e2.getX() - e1.getX();
float yDiff = e2.getY() - e1.getY();
try {
if(Math.abs(xDiff)>Math.abs(yDiff)){
if(Math.abs(xDiff)>threshold &&
Math.abs(velocityX)> velocity_threshold){
if(xDiff > 0){
//swipe right
Intent intent = new Intent(TopUpBalance.this, HomePage.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
finish();
}else{
//swipe left
}
return true;
}//you can handle swipe down and above here as well, the same way above
}
}catch (Exception e){
e.printStackTrace();
}
return false;
}
};
//init gesture
gestureDetector = new GestureDetector(listener);
view.setOnTouchListener(this);
}
#Override
public boolean onTouch(View view, MotionEvent motionEvent) {
return gestureDetector.onTouchEvent(motionEvent);
}
}
Declare your SwipeListener onCreate method as follow##
linearLayout = findViewById(R.id.layoutID);
//swipe
swipeListener = new SwipeListener(linearLayout);

Disable swipe on some fragments in ViewPager

I have a ViewPager that can disable or enable swipe touches:
public class ConfigurablePager extends ViewPager {
private final AtomicBoolean touchesAllowed = new AtomicBoolean();
...
private boolean touchesAllowed() {
return touchesAllowed.get();
}
public void enableTouches() {
touchesAllowed.set(true);
}
public void disableTouches() {
touchesAllowed.set(false);
}
#Override
public boolean onTouchEvent(MotionEvent ev) {
return touchesAllowed() && super.onTouchEvent(ev);
}
#Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
return touchesAllowed() && super.onInterceptTouchEvent(ev);
}
}
Some fragments can be swiped but other can't. Pager adapter aware of swipe behaviour for each fragment. This behaviour can be changed in ViewPager.OnPageChangeListener:
#Override
public void onPageSelected(int position) {
if (adapter.isTouchesAllowed(position)) {
views.pager.enableTouches();
} else {
views.pager.disableTouches();
}
}
The problem
Sometimes, when I swipe fragments very fast and click on tab for other fragment simultaneously viewpager can throw IllegalArgumentException:
FATAL EXCEPTION:
main java.lang.IllegalArgumentException: pointerIndex out of range
at android.view.MotionEvent.nativeGetAxisValue(Native Method)
at android.view.MotionEvent.getX(MotionEvent.java:1979)
at android.support.v4.view.MotionEventCompatEclair.getX(MotionEventCompatEclair.java:32)
at android.support.v4.view.MotionEventCompat$EclairMotionEventVersionImpl.getX(MotionEventCompat.java:110)
at android.support.v4.view.MotionEventCompat.getX(MotionEventCompat.java:462)
at android.support.v4.view.ViewPager.onTouchEvent(ViewPager.java:2080)
at com.test.debugpager.ConfigurablePager.onTouchEvent(ConfigurablePager.java:39)
at android.view.View.dispatchTouchEvent(View.java:7384)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2203)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1938)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2231)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1952)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2209)
It's happend because ViewPager save last pointerId and get inconsistent state (some touch events dropped by onInterceptTouchEvent) e.g. ACTION_MOVE with incorrect mActivePointerId from last touch event (see sources of ViewPager.java)
The question
Is it posible to disable swipe on some fragments in other way, maybe without overriding onInterceptTouchEvent?
ViewPager sources (onTouchEvent):
case MotionEvent.ACTION_MOVE:
if (!mIsBeingDragged) {
final int pointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);
final float x = MotionEventCompat.getX(ev, pointerIndex);
final float xDiff = Math.abs(x - mLastMotionX);
final float y = MotionEventCompat.getY(ev, pointerIndex);
final float yDiff = Math.abs(y - mLastMotionY);
if (DEBUG) Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff);
if (xDiff > mTouchSlop && xDiff > yDiff) {
if (DEBUG) Log.v(TAG, "Starting drag!");
mIsBeingDragged = true;
requestParentDisallowInterceptTouchEvent(true);
mLastMotionX = x - mInitialMotionX > 0 ? mInitialMotionX + mTouchSlop :
mInitialMotionX - mTouchSlop;
mLastMotionY = y;
setScrollState(SCROLL_STATE_DRAGGING);
setScrollingCacheEnabled(true);
// Disallow Parent Intercept, just in case
ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(true);
}
}
}

Solved
I've read intently android guide about gesture recognizing in a ViewGroup and analyzed ViewPager onTouchEvent sources. Here I recognize that ViewPager do swipe only for ACTION_MOVE event so we shouldn't call touch callbacks only for this action and we should obey base ViewGroup onInterceptTouchEvent result before calling base class onTouchEvent.
According to this rules I changed my ViewPager code:
#Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
if (touchesAllowed()) {
return super.onInterceptTouchEvent(ev);
} else {
if (MotionEventCompat.getActionMasked(ev) == MotionEvent.ACTION_MOVE) {
// ignore move action
} else {
if (super.onInterceptTouchEvent(ev)) {
super.onTouchEvent(ev);
}
}
return false;
}
}
#Override
public boolean onTouchEvent(MotionEvent ev) {
if (touchesAllowed()) {
return super.onTouchEvent(ev);
} else {
return MotionEventCompat.getActionMasked(ev) != MotionEvent.ACTION_MOVE && super.onTouchEvent(ev);
}
}

How to stop swipe at some point in ItemTouchHelpers?

I need to swipe an item at the beginning, or did a full swipe, or stopped in current point. As in the Yandex mail. I was tring to do setLeft(dx) and setRight(dx) but that's not what I need
I have class
ItemTouchHelperCallback extends ItemTouchHelper.Callback
and inside i override method
#Override
public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
View itemView = viewHolder.itemView;
// not sure why, but this method get's called for viewholder that are already swiped away
if (viewHolder.getAdapterPosition() == -1) {
// not interested in those
return;
}
float height = (float) itemView.getBottom() - (float) itemView.getTop();
float width = height / 3;
float temdX=0;
Bitmap icon;
if(dX > 0 || lastdX>0){
//try stop item while back in dx=0, but workin only while i debug
if(lastdX>=100 && dX==0 &&lastdX!=0 &&lastdX!=-720)
{
dX=100;
isCurrentlyActive=true;
}
lastdX=dX;
itemView.setLeft((int) dX);
p.setColor(Color.GREEN);
RectF background = new RectF((float) itemView.getLeft(), (float) itemView.getTop(), dX,(float) itemView.getBottom());
c.drawRect(background,p);
icon = BitmapFactory.decodeResource(mContext.getResources(), R.drawable.ic_y);
RectF icon_dest = new RectF((float) itemView.getLeft() + width ,(float) itemView.getTop() + width, (float) itemView.getLeft()+ 2*width,(float)itemView.getBottom() - width);
c.drawBitmap(icon, null, icon_dest, p);
} else if(lastdX<0 || dX<0) {
if(lastdX<=-100 && dX==0 &&lastdX!=0 &&lastdX!=720)
{
dX=-100;
//itemView.setTranslationX(-200);
isCurrentlyActive=true;
}
lastdX=dX;
itemView.setRight((int)(dX));
p.setColor(Color.RED);
RectF background = new RectF((float) itemView.getRight() + dX, (float) itemView.getTop(),(float) itemView.getRight(), (float) itemView.getBottom());
c.drawRect(background,p);
icon = BitmapFactory.decodeResource(mContext.getResources(), R.drawable.ic_x);
RectF icon_dest = new RectF((float) itemView.getRight() - 2*width ,(float) itemView.getTop() + width, (float) itemView.getRight() - width,(float)itemView.getBottom() - width);
c.drawBitmap(icon,null,icon_dest,p);
}
super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
}

I needed to do something similar and at the beginning I also thought to use the callbacks provided in the ItemTouchHelper. It turned out it's not the right approach.
If you want to stop (or in general to control) the translation of the view during the swipe, you need to be able to modify and save the value of the displacement dX. If you use the ItemTouchHelper, this value is controlled outside the available callbacks.
The solution for me was the implementation of the swipe with a custom touchListener, attached in the view holder of the recycler view. You can find an example of the basic implementation here. In case you need to consider the click on the item, remember you need to implement this in the touchListener as well.
I hope this is somehow helpful.
EDIT
Here a snippet of a custom ItemTouchListener. The listener is simplified and shows only code to handle the translation on the view during swipe. In order to stop swipe, just implement limit logic on translationX under ACTION_MOVE.
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
public class ItemTouchListener implements View.OnTouchListener {
private int mSlop;
private View mView;
private float mDownX, mDownY;
private boolean mSwiping;
private int mSwipingSlop;
private VelocityTracker mVelocityTracker;
private float mTranslationX;
public ItemTouchListener(View view) {
ViewConfiguration vc = ViewConfiguration.get(view.getContext());
mSlop = vc.getScaledTouchSlop();
mView = view;
}
#Override
public boolean onTouch(View view, MotionEvent motionEvent) {
// offset because the view is translated during swipe
motionEvent.offsetLocation(mTranslationX, 0);
switch (motionEvent.getActionMasked()) {
case MotionEvent.ACTION_DOWN: {
mDownX = motionEvent.getRawX();
mDownY = motionEvent.getRawY();
return true;
}
case MotionEvent.ACTION_UP: {
// if needed, implement part of limit swipe logic also here
if (mVelocityTracker == null) {
break;
}
mVelocityTracker.addMovement(motionEvent);
mVelocityTracker.computeCurrentVelocity(1000);
mVelocityTracker.recycle();
mVelocityTracker = null;
mTranslationX = 0;
mDownX = 0;
mDownY = 0;
mSwiping = false;
break;
}
case MotionEvent.ACTION_CANCEL: {
if (mVelocityTracker == null) {
break;
}
mVelocityTracker.recycle();
mVelocityTracker = null;
mTranslationX = 0;
mDownX = 0;
mDownY = 0;
mSwiping = false;
break;
}
case MotionEvent.ACTION_MOVE: {
if (mVelocityTracker == null) {
break;
}
mVelocityTracker.addMovement(motionEvent);
float deltaX = motionEvent.getRawX() - mDownX;
float deltaY = motionEvent.getRawY() - mDownY;
if (Math.abs(deltaX) > mSlop && Math.abs(deltaY) < Math.abs(deltaX) / 2) {
mSwiping = true;
mSwipingSlop = (deltaX > 0 ? mSlop : -mSlop);
// cancel view's touch
MotionEvent cancelEvent = MotionEvent.obtain(motionEvent);
cancelEvent.setAction(MotionEvent.ACTION_CANCEL |
(motionEvent.getActionIndex() << MotionEvent.ACTION_POINTER_INDEX_SHIFT));
cancelEvent.recycle();
}
if (mSwiping) {
// limit deltaX here: this will keep the swipe up to desired point
mTranslationX = deltaX;
mView.setTranslationX(deltaX - mSwipingSlop);
return true;
}
break;
}
}
return false;
}
}

Is it possible to make Imageview with checked and unchecked like radiobutton?

I am having nearly 500+ images in Imageview inside Horizontalscrollview. If i am selecting an image then I am marking it as selected. If I am selecting any other images in the view, it should be un-select and newly clicked image should have to be selected. How could I can achieve it?
for (int i = 0; i < Home.arr_category_item_list.size(); i++) {
ImageView circleImageView = new ImageView(getActivity());
imageLoader.get(Home.arr_category_item_list.get(i).get(Variables.EST_CATEGORY_ITEM_IMAGE), ImageLoader.getImageListener(circleImageView, R.drawable.defaultimage, R.drawable.defaultimage));
circleImageView.setTag(Integer.parseInt(Home.arr_category_item_list.get(i).get(Variables.EST_CATEGORY_ITEM_ID)));
circleImageView.setLayoutParams(params);
lnr_category_item.addView(circleImageView);
}
Please check the image attached. At the bottom of the screen there is an Image view. So user will have option to select only one image at a time.

Now this is some really old code, hope it still works.
Note: there may be a thing or two missing, but you can get the idea from this implementation
import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ImageView;
import yourpackage.R;
//Creataed by Bojan Kseneman on 14.8.2013
public class CustomCheckBox extends ImageView {
private boolean isChecked;
private boolean isImageShown;
private boolean useCustomClickListener;
//private String android_xmlns = "http://schemas.android.com/apk/res/android";
private String app_xmlns;
private int checkboxOnResID;
private int checkboxOffResID;
private int checkboxDisabledOnResID;
private int checkboxDisabledOffResID;
//private int imageHeight;
//private int imageWidth;
public CustomCheckBox(Context context, AttributeSet attrs) {
super(context, attrs);
app_xmlns = new StringBuilder("http://schemas.android.com/apk/res/" + context.getPackageName()).toString();
init(attrs);
}
private void init(AttributeSet attrs) {
checkboxOnResID = attrs.getAttributeResourceValue(app_xmlns, "resourceChecked", R.drawable.round_checkbox_on);
checkboxOffResID = attrs.getAttributeResourceValue(app_xmlns, "resourceNotChecked", R.drawable.round_checkbox_off);
checkboxDisabledOnResID = attrs.getAttributeResourceValue(app_xmlns, "resourceDisabledOn", R.drawable.round_checkbox_off);
checkboxDisabledOffResID = attrs.getAttributeResourceValue(app_xmlns, "resourceDisabledOff", R.drawable.round_checkbox_off);
useCustomClickListener = attrs.getAttributeBooleanValue(app_xmlns, "customClickEvent", false);
if (useCustomClickListener)
this.setOnTouchListener(new CboxTouchListener());
else {
this.setOnTouchListener(new NormalClickListener());
}
if (!hasOnClickListener()) {
/**
* assign a new onClick listener so we get desired onClick sound
* effect (because we call it) this is opposite to how android
* behaves, where you don't hear the sound if there is not
* onClickListener assigned
*/
this.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
}
});
}
}
private boolean hasOnClickListener() {
try {
if (android.os.Build.VERSION.SDK_INT >= 14) {
//the information is inside ListenerInfo
java.lang.reflect.Field listenerInfoField = null;
listenerInfoField = Class.forName("android.view.View").getDeclaredField("mListenerInfo");
if (listenerInfoField != null)
listenerInfoField.setAccessible(true);
Object mOnClickListener = null;
mOnClickListener = listenerInfoField.get(this); //get from view object, in this case this is this
// get the field mOnClickListener, that holds the listener and cast it to a listener
java.lang.reflect.Field listenerField = null;
listenerField = Class.forName("android.view.View$ListenerInfo").getDeclaredField("mOnClickListener");
//View.OnClickListener myListener = (View.OnClickListener) listenerField.get(myLiObject);
return (listenerField.get(mOnClickListener) != null);
}
else {
//directly in View
java.lang.reflect.Field f = Class.forName("android.view.View").getDeclaredField("mOnClickListener");
return (f.get(this) != null);
}
}
catch (Exception e) {
return false;
}
}
// private void setScaledDownImage(int resID) {
// this.setImageBitmap(CommonMethods.decodeSampledBitmapFromResource(getContext(), resID, imageWidth, imageHeight));
// }
public boolean isChecked() {
return (isChecked && this.isEnabled());
}
public void setChecked(boolean isChecked) {
if (this.isEnabled())
setCheckedIgnoreEnabled(isChecked);
else
this.setEnabled(false);
}
public void setCheckedIgnoreEnabled(boolean isChecked) {
if ((this.isChecked != isChecked) || !isImageShown) {
this.isChecked = isChecked;
if (isChecked)
setImageResource(checkboxOnResID);
else
setImageResource(checkboxOffResID);
}
}
#Override
public void setEnabled(boolean enabled) {
super.setEnabled(enabled);
if (enabled)
setChecked(isChecked);
else {
int resID = isChecked ? checkboxDisabledOnResID : checkboxDisabledOffResID;
setImageResource(resID);
}
}
public void setCheckedAndEnabled(boolean isChecked, boolean isEnabled) {
setCheckedIgnoreEnabled(isChecked);
setEnabled(isEnabled);
}
public void toggle() {
setChecked(!isChecked);
}
public void toggleWithClick() {
toggle();
this.performClick();
}
public void toggleWithSilentClick() {
//v.playSoundEffect(android.view.SoundEffectConstants.CLICK);
boolean currentState = this.isSoundEffectsEnabled();
this.setSoundEffectsEnabled(false);
toggleWithClick();
this.setSoundEffectsEnabled(currentState);
}
private class CboxTouchListener extends ImageBoundClickListener {
#Override
public void doSomething() {
super.doSomething();
setChecked(!isChecked);
CustomCheckBox.this.performClick();
}
}
private class NormalClickListener extends MyOnClickListener {
#Override
public void doSomething() {
super.doSomething();
setChecked(!isChecked);
CustomCheckBox.this.performClick();
}
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
//this.imageWidth = MeasureSpec.getSize(widthMeasureSpec);
//this.imageHeight = MeasureSpec.getSize(heightMeasureSpec);
if (!isImageShown) {
setChecked(isChecked);
isImageShown = !isImageShown;
}
}
}
I used this click listener, since I was using some round images and I didn't want to trigger the click events when the user clicked on the transparent part of the image.
public abstract class ImageBoundClickListener implements android.view.View.OnTouchListener {
private String TAG = "ImageBoundsTouchListener";
private boolean shouldTriggerAction = false;
Rect allowedArea;
#Override
public boolean onTouch(View v, MotionEvent event) {
//let's us detect only clicks on the part where actual image is and not where the ImageView is
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
float[] eventXY = new float[] { event.getX(), event.getY() };
allowedArea = new Rect(v.getLeft(), v.getTop(), v.getRight(), v.getBottom());
android.graphics.Matrix invertMatrix = new android.graphics.Matrix();
ImageView iv = (ImageView) v;
iv.getImageMatrix().invert(invertMatrix);
invertMatrix.mapPoints(eventXY);
int x = (int) eventXY[0];
int y = (int) eventXY[1];
Drawable imgDrawable = iv.getDrawable();
Bitmap bitmap = ((BitmapDrawable) imgDrawable).getBitmap();
//Limit x,y within the bitmap
if (x < 0)
x = 0;
else if (x > (bitmap.getWidth() - 1))
x = bitmap.getWidth() - 1;
if (y < 0)
y = 0;
else if (y > bitmap.getHeight() - 1)
y = bitmap.getHeight() - 1;
int touchedRGB = bitmap.getPixel(x, y);
//is transparent?
shouldTriggerAction = (touchedRGB == 0) ? false : true;
return true;
case MotionEvent.ACTION_MOVE:
if (!allowedArea.contains(v.getLeft() + (int) event.getX(), v.getTop() + (int) event.getY()))
//the user went out of the user area
shouldTriggerAction = false;
return true;
case MotionEvent.ACTION_UP:
//finger is no longer on screen
if (shouldTriggerAction)
doSomething();
return true;
default:
return false;
}
}
public void doSomething() {
}
}

How to Zoom a Text View in Scroll View?

I have seen a lots of code here which is helpful to zoom your textview but none of them work with my text because it is within scrollview. How can I get rid of this problem?
import android.app.Activity;
import android.os.Bundle;
import android.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.TextView;
public class Introduce extends Activity implements OnTouchListener{
final static float STEP = 200;
TextView mtxtRatio1,mtxtRatio2,mtxtRatio3,mtxtRatio4;
float mRatio = 1.0f;
int mBaseDist;
float mBaseRatio;
float fontsize = 13;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.introduce);
mtxtRatio1 = (TextView)findViewById(R.id.intro1);
mtxtRatio1.setTextSize(mRatio+13);
}
public boolean onTouchEvent(MotionEvent event) {
if (event.getPointerCount() == 2) {
int action = event.getAction();
int pureaction = action & MotionEvent.ACTION_MASK;
if (pureaction == MotionEvent.ACTION_POINTER_DOWN) {
mBaseDist = getDistance(event);
mBaseRatio = mRatio;
} else {
float delta = (getDistance(event) - mBaseDist) / STEP;
float multi = (float)Math.pow(2, delta);
mRatio = Math.min(1024.0f, Math.max(0.1f, mBaseRatio * multi));
mtxtRatio1.setTextSize(mRatio+13);
}
}
return true;
}
int getDistance(MotionEvent event) {
int dx = (int)(event.getX(0) - event.getX(1));
int dy = (int)(event.getY(0) - event.getY(1));
return (int)(Math.sqrt(dx * dx + dy * dy));
}
public boolean onTouch(View v, MotionEvent event) {
// TODO Auto-generated method stub
return false;
}
}

Following is the way for implementing Pinch Zoom in TextView with/without ScrollView
MainActivity.java
public class MainActivity extends AppCompatActivity{
final static float STEP = 200;
float mRatio = 1.0f;
int mBaseDist;
float mBaseRatio;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
textViewData = (TextView).findViewById(R.id.tvContributeData);
textViewData.setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View view, MotionEvent event) {
if (event.getPointerCount() == 2) {
int action = event.getAction();
int pureaction = action & MotionEvent.ACTION_MASK;
if (pureaction == MotionEvent.ACTION_POINTER_DOWN) {
mBaseDist = getDistance(event);
mBaseRatio = mRatio;
} else {
float delta = (getDistance(event) - mBaseDist) / STEP;
float multi = (float) Math.pow(2, delta);
mRatio = Math.min(1024.0f, Math.max(0.1f, mBaseRatio * multi));
textViewData.setTextSize(mRatio + 13);
}
}
return true;
});
int getDistance(MotionEvent event) {
int dx = (int) (event.getX(0) - event.getX(1));
int dy = (int) (event.getY(0) - event.getY(1));
return (int) (Math.sqrt(dx * dx + dy * dy));
}
}
}

Use Polidea's zoomview, it works in a scrollview and has pinch zoom and double tap to zoom, one thing thought, I ended up disabling the pinch zoom and just using the double tap
https://github.com/Polidea/android-zoom-view
Put your TextView andany other Views you are using into a LinearLayout that lives on a ZoomView which lives on the ScrollView, e.g.:
<ScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content">
<com.polidea.ZoomView
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<LinearLayout
android:id="#+id/myLinearLayout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical" >
</LinearLayout>
</com.polidea.ZoomView>
</ScrollView>

Hopefully this will help others. This answer is from here and here.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tv = (TextView) findViewById(R.id.tv);
tv.setText(getString(R.string.hello_world));
scaleGestureDetector = new ScaleGestureDetector(this, new simpleOnScaleGestureListener());
tv.setOnTouchListener(new OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
if(event.getPointerCount() == 1){
//stuff for 1 pointer
}else{ //when 2 pointers are present
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
// Disallow ScrollView to intercept touch events.
v.getParent().requestDisallowInterceptTouchEvent(true);
scaleGestureDetector.onTouchEvent(event);
break;
case MotionEvent.ACTION_MOVE:
// Disallow ScrollView to intercept touch events.
v.getParent().requestDisallowInterceptTouchEvent(true);
scaleGestureDetector.onTouchEvent(event);
break;
case MotionEvent.ACTION_UP:
// Allow ScrollView to intercept touch events.
v.getParent().requestDisallowInterceptTouchEvent(false);
break;
}
}
return true;
}
});
}
The answer from here has the problem when text is resized even fingers are static (two fingers on the screen). What I did is add a check so that the textSize do not make any changes instantly.
private float safe;
public class simpleOnScaleGestureListener extends SimpleOnScaleGestureListener {
#Override
public boolean onScale(ScaleGestureDetector detector) {
// TODO Auto-generated method stub
float size = tv.getTextSize();
Log.d("TextSizeStart", String.valueOf(size));
//float factor = detector.getScaleFactor();
float factor = Math.max(0.5f, Math.min(detector.getScaleFactor(), 2f));
Log.d("Factor", String.valueOf(factor));
float product = size*factor;
Log.d("TextSize", String.valueOf(product));
safe = Math.abs(product - size);
if(product <= 100 && product >= 20 && safe < 3){
//tv.setText("factor= " +factor + "\n" + "product = \n" + size + " * " + factor + " \n= " + product +"\n" + getString(R.string.hello_world));
tv.setTextSize(TypedValue.COMPLEX_UNIT_PX, product);
}
size = tv.getTextSize();
Log.d("TextSizeEnd", String.valueOf(size));
return true;
}
}
You can play around with safe < 3 to your desired changes value.

I'm using this solution.
Crédits for Zoom Algorithm in this vídeo
Use a TextView without ScrollView, just use android:scrollbars="vertical"
<TextView
android:id="#+id/activity_content_text_content"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_weight="1"
android:gravity="fill"
android:textSize="8pt"
android:scrollbars="vertical"
/>
Java:
public class MainActivity extends Activity implements View.OnTouchListener {
private TextView textContent = null;
private final static float move = 200;
private float ratio = 1.0f;
private int baseDist;
private float baseRatio;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.teste_layout);
textContent = findViewById(R.id.activity_content_text_content);
textContent.setText("Lorem ipsum dolor sit amet......");
textContent.setMovementMethod(new ScrollingMovementMethod());
textContent.setOnTouchListener(this);
}
#Override
public boolean onTouch(View v, MotionEvent event) {
return onTouchEvent(event);
}
#Override
public boolean onTouchEvent(MotionEvent event) {
if(event.getPointerCount() == 2){
int action = event.getAction();
int mainAction = action&MotionEvent.ACTION_MASK;
if(mainAction == MotionEvent .ACTION_POINTER_DOWN){
baseDist = getDisTance(event);
baseRatio = ratio;
} else {
float scale = (getDisTance(event)-baseDist)/move;
float factor = (float)Math.pow(2, scale);
ratio = Math.min(1024.0f, Math.max(0.1f, baseRatio*factor));
textContent.setTextSize(ratio+15);
}
} else {
return false;
}
return true;
}
private int getDisTance(MotionEvent event) {
int dx = (int) (event.getX(0)-event.getX(1));
int dy = (int) (event.getY(0)-event.getY(1));
return (int) (Math.sqrt(dx*dx+dy*dy));
}
}