Pinch Zooming on textview android

Question

Hello friend I have done pinch zoom textview and its work fine but the problem is when I zoom out the textview position changed and i want the position of textview is fixed

Answer 1

public class MainActivity extends Activity {

TextView scaleGesture;
ScaleGestureDetector scaleGestureDetector;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    scaleGesture = (TextView)findViewById(R.id.article);
    scaleGesture.setText("this is some text");
    scaleGestureDetector = new ScaleGestureDetector(this, new simpleOnScaleGestureListener());
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}


@Override
public boolean onTouchEvent(MotionEvent event) {
    // TODO Auto-generated method stub
    scaleGestureDetector.onTouchEvent(event);
    return true;
}

public class simpleOnScaleGestureListener extends
        SimpleOnScaleGestureListener {

    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        // TODO Auto-generated method stub
        float size = scaleGesture.getTextSize();
        Log.d("TextSizeStart", String.valueOf(size));

        float factor = detector.getScaleFactor();
        Log.d("Factor", String.valueOf(factor));


        float product = size*factor;
        Log.d("TextSize", String.valueOf(product));
        scaleGesture.setTextSize(TypedValue.COMPLEX_UNIT_PX, product);

        size = scaleGesture.getTextSize();
        Log.d("TextSizeEnd", String.valueOf(size));
        return true;
    }
}
 }

View

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >
<TextView
    android:id="@+id/article"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

Answer 2

Please use below code:

public class TouchExampleView extends View {

private static final int INVALID_POINTER_ID = -1;

private Drawable mIcon;
private float mPosX;
private float mPosY;

private float mLastTouchX;
private float mLastTouchY;
private int mActivePointerId = INVALID_POINTER_ID;

private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;

public TouchExampleView(Context context) {
    this(context, null, 0);
}

public TouchExampleView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public TouchExampleView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    mIcon = context.getResources().getDrawable(R.drawable.toggle);
    mIcon.setBounds(0, 0, mIcon.getIntrinsicWidth(),
            mIcon.getIntrinsicHeight());

    mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
}

@Override
public boolean onTouchEvent(MotionEvent ev) {
    // Let the ScaleGestureDetector inspect all events.
    mScaleDetector.onTouchEvent(ev);

    final int action = ev.getAction();
    switch (action & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_DOWN: {
        final float x = ev.getX();
        final float y = ev.getY();

        mLastTouchX = x;
        mLastTouchY = y;
        mActivePointerId = ev.getPointerId(0);
        break;
    }

    case MotionEvent.ACTION_MOVE: {
        final int pointerIndex = ev.findPointerIndex(mActivePointerId);
        final float x = ev.getX(pointerIndex);
        final float y = ev.getY(pointerIndex);

        // Only move if the ScaleGestureDetector isn't processing a gesture.
        if (!mScaleDetector.isInProgress()) {
            final float dx = x - mLastTouchX;
            final float dy = y - mLastTouchY;

            mPosX += dx;
            mPosY += dy;

            invalidate();
        }

        mLastTouchX = x;
        mLastTouchY = y;

        break;
    }

    case MotionEvent.ACTION_UP: {
        mActivePointerId = INVALID_POINTER_ID;
        break;
    }

    case MotionEvent.ACTION_CANCEL: {
        mActivePointerId = INVALID_POINTER_ID;
        break;
    }

    case MotionEvent.ACTION_POINTER_UP: {
        final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
        final int pointerId = ev.getPointerId(pointerIndex);
        if (pointerId == mActivePointerId) {
            // This was our active pointer going up. Choose a new
            // active pointer and adjust accordingly.
            final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
            mLastTouchX = ev.getX(newPointerIndex);
            mLastTouchY = ev.getY(newPointerIndex);
            mActivePointerId = ev.getPointerId(newPointerIndex);
        }
        break;
    }
    }

    return true;
}

@Override
public void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    canvas.save();
    canvas.translate(mPosX, mPosY);
    canvas.scale(mScaleFactor, mScaleFactor);
    Paint paint = new Paint(); 
    paint.setStyle(Style.FILL);  
    paint.setColor(Color.BLACK); 
    paint.setTextSize(20); 
    canvas.drawText("Hello how are you", mPosX, mPosY, paint);
    mIcon.draw(canvas);
    canvas.restore();
}

private class ScaleListener extends
        ScaleGestureDetector.SimpleOnScaleGestureListener {
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        mScaleFactor *= detector.getScaleFactor();

        // Don't let the object get too small or too large.
        mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 5.0f));

        invalidate();
        return true;
    }
}

}

Answer 3

I have done this way:

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/mytv"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:text="This is my sample text for pinch zoom demo, you can zoom in and out using pinch zoom, thanks" />

</RelativeLayout>

MainActivity.java:

import android.app.Activity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.TextView;

public class MyTextViewPinchZoomClass extends Activity implements OnTouchListener {

    final static float STEP = 200;
    TextView mytv;
    float mRatio = 1.0f;
    int mBaseDist;
    float mBaseRatio;
    float fontsize = 13;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mytv = (TextView) findViewById(R.id.mytv);
        mytv.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));
                mytv.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) {
        return false;
    }
}

Done