ImageView 缩放

 <ImageView

                android:id="@+id/imageview"

                android:layout_width="wrap_content"

                android:layout_height="wrap_content"

                android:src="@drawable/zixun"

                android:scaleType="matrix"

                />

关键点：缩放的内容不能是图片的背景，一定要是图片的内容

public class HelpActivity extends Activity

{

    private static final int NONE = 0;

    private static final int DRAG = 1;

    private static final int ZOOM = 2;

    private int mode = NONE;

    private float oldDist;

    private Matrix matrix = new Matrix();

    private Matrix savedMatrix = new Matrix();

    private PointF start = new PointF();

    private PointF mid = new PointF();

    protected void onCreate(Bundle savedInstanceState)

    {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.help);

        ImageView view = (ImageView) findViewById(R.id.imageview);

//        view.setImageResource(R.drawable.icon);

        view.setOnTouchListener(mOnTouchListener);

    }

    OnTouchListener mOnTouchListener = new OnTouchListener()

    {

        public boolean onTouch(View v, MotionEvent event)

        {

            Trace.Log("------------------"+event.toString());

            ImageView view = (ImageView) v;

            switch (event.getAction() & MotionEvent.ACTION_MASK)

            {

            case MotionEvent.ACTION_DOWN:

                savedMatrix.set(matrix);

                start.set(event.getX(), event.getY());

                mode = DRAG;

                break;

            case MotionEvent.ACTION_UP:

            case MotionEvent.ACTION_POINTER_UP:

                mode = NONE;

                break;

            // 多点触控

            case MotionEvent.ACTION_POINTER_DOWN:

                oldDist = spacing(event);

                if (oldDist > 10f)

                {

                    savedMatrix.set(matrix);

                    midPoint(mid, event);

                    mode = ZOOM;

                }

                break;

            case MotionEvent.ACTION_MOVE:

                if (mode == DRAG)

                {

                    matrix.set(savedMatrix);

                    matrix.postTranslate(event.getX() - start.x, event.getY() - start.y);

                }

                else if (mode == ZOOM)

                {

                    float newDist = spacing(event);

                    if (newDist > 10f)

                    {

                        matrix.set(savedMatrix);

                        float scale = newDist / oldDist;

                        matrix.postScale(scale, scale, mid.x, mid.y);

                        Trace.Log("------------------"+newDist);

                    }

                }

                break;

            }

            view.setImageMatrix(matrix);

//            view.invalidate();

            return true;

        }

    };

    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);

    }

    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);

    }

    public void onClickBack(View view)

    {

        backToCardSelect();

    }

}

ImageVIew 需要在最上面一层，否则可能不会生效