android中手势操作图片的平移、缩放、旋转

在网上搜到很多都是一样的版本，只有平移和缩放的功能。我在搜到的源代码基础上添加了旋转和边界检查的功能。

代码主要分两部分，一个activity一个view，代码如下：

[java]
package com.example.touch;

import android.app.Activity;
import android.os.Bundle;

public class TouchImageViewActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        TouchImageView img = new TouchImageView(this);
        setContentView(img);
    }
}

[java]
package com.example.touch;

import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.util.DisplayMetrics;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.widget.ImageView;

public class TouchImageView extends ImageView {

    float x_down = 0;
    float y_down = 0;
    PointF start = new PointF();
    PointF mid = new PointF();
    float oldDist = 1f;
    float oldRotation = 0;
    Matrix matrix = new Matrix();
    Matrix matrix1 = new Matrix();
    Matrix savedMatrix = new Matrix();

    private static final int NONE = 0;
    private static final int DRAG = 1;
    private static final int ZOOM = 2;
    int mode = NONE;

    boolean matrixCheck = false;

    int widthScreen;
    int heightScreen;

    Bitmap gintama;

    public TouchImageView(TouchImageViewActivity activity) {
        super(activity);
        gintama = BitmapFactory.decodeResource(getResources(), R.drawable.gintama);

        DisplayMetrics dm = new DisplayMetrics();
        activity.getWindowManager().getDefaultDisplay().getMetrics(dm);
        widthScreen = dm.widthPixels;
        heightScreen = dm.heightPixels;

        matrix = new Matrix();
    }

    protected void onDraw(Canvas canvas) {
        canvas.save();
        canvas.drawBitmap(gintama, matrix, null);
        canvas.restore();
    }

    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN:
            mode = DRAG;
            x_down = event.getX();
            y_down = event.getY();
            savedMatrix.set(matrix);
            break;
        case MotionEvent.ACTION_POINTER_DOWN:
            mode = ZOOM;
            oldDist = spacing(event);
            oldRotation = rotation(event);
            savedMatrix.set(matrix);
            midPoint(mid, event);
            break;
        case MotionEvent.ACTION_MOVE:
            if (mode == ZOOM) {
                matrix1.set(savedMatrix);
                float rotation = rotation(event) - oldRotation;
                float newDist = spacing(event);
                float scale = newDist / oldDist;
                matrix1.postScale(scale, scale, mid.x, mid.y);// 縮放
                matrix1.postRotate(rotation, mid.x, mid.y);// 旋轉
                matrixCheck = matrixCheck();
                if (matrixCheck == false) {
                    matrix.set(matrix1);
                    invalidate();
                }
            } else if (mode == DRAG) {
                matrix1.set(savedMatrix);
                matrix1.postTranslate(event.getX() - x_down, event.getY()
                        - y_down);// 平移
                matrixCheck = matrixCheck();
                matrixCheck = matrixCheck();
                if (matrixCheck == false) {
                    matrix.set

补充：移动开发 , Android ,