在android中为放大和缩小添加限制 [英] Add limit to zoom-in and zoom-out in android

问题描述

我有一个可以缩放的图像视图.我有一个运行良好的代码，但我的问题是我想为最大和最小缩放级别添加限制.

I have an imageview that can be zoomed. I have a code that works well, but my problem is that I want to add a limit for maximum and minimum zooming levels.

import android.annotation.TargetApi;
import android.app.ActionBar;
import android.app.Activity;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.os.Build;
import android.os.Bundle;
import android.util.FloatMath;
import android.util.Log;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.ImageView;

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public class Reach extends Activity implements OnTouchListener
{
    private static final String TAG = "Touch";
    @SuppressWarnings("unused")
    private static final float MIN_ZOOM = 1f,MAX_ZOOM = 1f;

// These matrices will be used to scale points of the image
Matrix matrix = new Matrix();
Matrix savedMatrix = new Matrix();

// The 3 states (events) which the user is trying to perform
static final int NONE = 0;
static final int DRAG = 1;
static final int ZOOM = 2;
int mode = NONE;

// these PointF objects are used to record the point(s) the user is touching
PointF start = new PointF();
PointF mid = new PointF();
float oldDist = 1f;

@Override
protected void onCreate(Bundle savedInstanceState)
{
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.reach_us);
    int currentAPIVersion = android.os.Build.VERSION.SDK_INT;

    if (currentAPIVersion >= android.os.Build.VERSION_CODES.HONEYCOMB) 
    {

        // RUN THE CODE SPECIFIC TO THE API LEVELS ABOVE HONEYCOMB (API 11+)   
        ActionBar actionBar = getActionBar();
        actionBar.setDisplayHomeAsUpEnabled(true);
    }
    ImageView view=(ImageView)findViewById(R.id.map);
    view.setOnTouchListener(this);
}

@Override
public boolean onOptionsItemSelected(MenuItem item)
{

    switch (item.getItemId()) {

    case android.R.id.home: {
        this.finish();

        return true;
    }

    default:
        return super.onOptionsItemSelected(item);
    }
}
@Override
public boolean onTouch(View v, MotionEvent event) 
{
    ImageView view = (ImageView) v;
    view.setScaleType(ImageView.ScaleType.MATRIX);
    float scale;

    dumpEvent(event);
    // Handle touch events here...

    switch (event.getAction() & MotionEvent.ACTION_MASK) 
    {
    case MotionEvent.ACTION_DOWN:   // first finger down only
        savedMatrix.set(matrix);
        start.set(event.getX(), event.getY());
        Log.d(TAG, "mode=DRAG"); // write to LogCat
        mode = DRAG;
        break;

    case MotionEvent.ACTION_UP: // first finger lifted

    case MotionEvent.ACTION_POINTER_UP: // second finger lifted

        mode = NONE;
        Log.d(TAG, "mode=NONE");
        break;

    case MotionEvent.ACTION_POINTER_DOWN: // first and second finger down

        oldDist = spacing(event);
        Log.d(TAG, "oldDist=" + oldDist);
        if (oldDist > 5f) {
            savedMatrix.set(matrix);
            midPoint(mid, event);
            mode = ZOOM;
            Log.d(TAG, "mode=ZOOM");
        }
        break;

    case MotionEvent.ACTION_MOVE:

        if (mode == DRAG) 
        { 
            matrix.set(savedMatrix);
            matrix.postTranslate(event.getX() - start.x, event.getY() - start.y); // create the transformation in the matrix  of points
        } 
        else if (mode == ZOOM) 
        { 
            // pinch zooming
            float newDist = spacing(event);
            Log.d(TAG, "newDist=" + newDist);
            if (newDist > 5f) 
            {
                matrix.set(savedMatrix);
                scale = newDist / oldDist; // setting the scaling of the
                // matrix...if scale > 1 means
                // zoom in...if scale < 1 means
                // zoom out
                matrix.postScale(scale, scale, mid.x, mid.y);
            }
        }
        break;
    }

    view.setImageMatrix(matrix); // display the transformation on screen

    return true; // indicate event was handled
}

/*
 * --------------------------------------------------------------------------
 * Method: spacing Parameters: MotionEvent Returns: float Description:
 * checks the spacing between the two fingers on touch
 * ----------------------------------------------------
 */

private float spacing(MotionEvent event) 
{
    float x = event.getX(0) - event.getX(1);
    float y = event.getY(0) - event.getY(1);
    return FloatMath.sqrt(x * x + y * y);
}

/*
 * --------------------------------------------------------------------------
 * Method: midPoint Parameters: PointF object, MotionEvent Returns: void
 * Description: calculates the midpoint between the two fingers
 * ------------------------------------------------------------
 */

private void midPoint(PointF point, MotionEvent event) 
{
    float x = event.getX(0) + event.getX(1);
    float y = event.getY(0) + event.getY(1);
    point.set(x / 2, y / 2);
}

/** Show an event in the LogCat view, for debugging */
private void dumpEvent(MotionEvent event) 
{
    String names[] = { "DOWN", "UP", "MOVE", "CANCEL", "OUTSIDE","POINTER_DOWN", "POINTER_UP", "7?", "8?", "9?" };
    StringBuilder sb = new StringBuilder();
    int action = event.getAction();
    int actionCode = action & MotionEvent.ACTION_MASK;
    sb.append("event ACTION_").append(names[actionCode]);

    if (actionCode == MotionEvent.ACTION_POINTER_DOWN || actionCode == MotionEvent.ACTION_POINTER_UP) 
    {
        sb.append("(pid ").append(action >> MotionEvent.ACTION_POINTER_ID_SHIFT);
        sb.append(")");
    }

    sb.append("[");
    for (int i = 0; i < event.getPointerCount(); i++) 
    {
        sb.append("#").append(i);
        sb.append("(pid ").append(event.getPointerId(i));
        sb.append(")=").append((int) event.getX(i));
        sb.append(",").append((int) event.getY(i));
        if (i + 1 < event.getPointerCount())
            sb.append(";");
    }

    sb.append("]");
    Log.d("Touch Events ---------", sb.toString());
}
}

我看到了很多问题&与此相关的答案，但没有人真正帮助我.请给我一个解决方案.提前致谢

I have seen lot of question & answers linked with this, but no one really helps me. Please give me a solution. Thanks in advance

推荐答案

我有一个解决方案.但它似乎并不完美.只需在切换案例之后和 view.setImageMatrix(matrix); 之前添加下面给出的方法方法如下:

I got a solution for this. But its not seems to be perfect one. Just add the methods given below after the switch cases and just before the view.setImageMatrix(matrix); here is the methods:

private void limitZoom(Matrix m) {

        float[] values = new float[9];
        m.getValues(values);
        float scaleX = values[Matrix.MSCALE_X];
        float scaleY = values[Matrix.MSCALE_Y];
        if(scaleX > MAX_ZOOM) {
            scaleX = MAX_ZOOM;
        } else if(scaleX < MIN_ZOOM) {
            scaleX = MIN_ZOOM;
        }

        if(scaleY > MAX_ZOOM) {
            scaleY = MAX_ZOOM;
        } else if(scaleY < MIN_ZOOM) {
            scaleY = MIN_ZOOM;
        }

        values[Matrix.MSCALE_X] = scaleX;
        values[Matrix.MSCALE_Y] = scaleY; 
        m.setValues(values);
    }

    private void limitDrag(Matrix m) {
        float[] values = new float[9];
        m.getValues(values);
        float transX = values[Matrix.MTRANS_X];
        float transY = values[Matrix.MTRANS_Y];
        float scaleX = values[Matrix.MSCALE_X];
        float scaleY = values[Matrix.MSCALE_Y];

        ImageView iv = (ImageView)findViewById(R.id.map);
        Rect bounds = iv.getDrawable().getBounds();
        int viewWidth = getResources().getDisplayMetrics().widthPixels;
        int viewHeight = getResources().getDisplayMetrics().heightPixels;

        int width = bounds.right - bounds.left;
        int height = bounds.bottom - bounds.top;

        float minX = (-width + 20) * scaleX; 
        float minY = (-height + 20) * scaleY;

        if(transX > (viewWidth - 20)) {
            transX = viewWidth - 20;
        } else if(transX < minX) {
            transX = minX;
        }

        if(transY > (viewHeight - 80)) {
            transY = viewHeight - 80;
        } else if(transY < minY) {
            transY = minY;
        }

        values[Matrix.MTRANS_X] = transX;
        values[Matrix.MTRANS_Y] = transY; 
        m.setValues(values);

    }

还有比这个更好的解决方案吗?

Is there is any other solution better than this one?

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