因爲在Android中不允許ImageView在產生後，動態修改其長度與寬度，所以爲了實現圖片放大、縮小的功能，使用的方式是當用戶在單擊放大或縮小的按鈕時，除了將圖片作放大或縮小的動作外，並將原來Layout中的ImageView刪除，重新產生一個新的ImageView，指定圖片給它後，再放入Layout裏。用戶看起來，就好像是同一張圖片在放大或縮小。
在放大、縮小圖片文件時使用的Martix對象，除了可以用來作圖片的縮放外，還有非常實用的旋轉效果.下面包含兩種方法imageview.setImageBitmap和setImageMatrix,注意兩者的細小區別，前者需要再次setContentView包含imageView的父佈局，而後者則不需要，但是這只是imageView的父佈局爲佈局文件的根節點的情況。實例如下：
public class CBI_Activity extends Activity {
private ImageView img;
private ZoomControls zControls;
private FrameLayout layout;
private float zoomin = (float) 1.2;
private float zoomout = (float) 0.8;
private float scaleHeight = 1;
private float scaleWdith = 1;
private Bitmap bitmap;
private int id = 0;//在java代碼添加控件，也需要給控件添加id，便於刪除操作
private int displayWidth;
private int displayHeight;
private int height_one;
private int width_one;
private ImageViewTouchListener listener;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.cbimgdisplay);
listener = new ImageViewTouchListener();
DisplayMetrics dm = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(dm);
displayWidth = dm.widthPixels;
/* 屏幕高度須扣除下方Button高度 */
displayHeight = dm.heightPixels - 80;
img = (ImageView) findViewById(R.id.cbidisplay);
layout = (FrameLayout) findViewById(R.id.layout);
Intent intent = getIntent();
String imgName = (String) intent.getExtras().get("imgName");
bitmap = ImgUtil.getBitmapByFilename(imgName);
img.setImageBitmap(bitmap);
img.setOnTouchListener(listener);
zControls = (ZoomControls) this.findViewById(R.id.zoomControls1);
// zControls.setEnabled(true);//
zControls.setOnZoomInClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(CBI_Activity.this,
"縮小," + scaleWdith + "," + scaleHeight,
Toast.LENGTH_SHORT).show();
bigImg();
}
private void bigImg() {
width_one = bitmap.getWidth();
height_one = bitmap.getHeight();
if (width_one > displayWidth || height_one > displayHeight) {
Toast.makeText(CBI_Activity.this,
"放大已經超過了屏幕的尺寸，不能再放大" + scaleWdith,
Toast.LENGTH_SHORT).show();
} else {
scaleWdith *= zoomin;
scaleHeight *= zoomin;
resizeImg();
}
}
});
zControls.setOnZoomOutClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
smallImg();
}
private void smallImg() {
width_one = bitmap.getWidth();
height_one = bitmap.getHeight();
scaleWdith *= zoomout;
scaleHeight *= zoomout;
resizeImg();
Toast.makeText(CBI_Activity.this,
"縮小," + scaleWdith + "," + scaleHeight,
Toast.LENGTH_SHORT).show();
}
});
}
public void resizeImg() {
Matrix matrix = new Matrix();
matrix.postScale(scaleWdith, scaleHeight);
Bitmap bitmapTwo = Bitmap.createBitmap(bitmap, 0, 0, width_one,
height_one, matrix, true);
if (id == 0) {
// 第一次刪除
layout.removeView(img);
} else {
layout.removeView(CBI_Activity.this.findViewById(id));
}
id++;
ImageView imgTwo = new ImageView(CBI_Activity.this);
imgTwo.setImageBitmap(bitmapTwo);
imgTwo.setId(id);
imgTwo.setOnTouchListener(listener);
layout.addView(imgTwo, 3);
CBI_Activity.this.setContentView(layout);
Toast.makeText(CBI_Activity.this,
"放大," + scaleWdith + "," + scaleHeight, Toast.LENGTH_SHORT)
.show();
}
private final static int NONE = 0;
private final static int DRAG = 1;// 一隻手
private final static int ZOOM = 2;// 多點觸摸
private Matrix matrix = new Matrix();// 保存拖拉變化的矩陣
private Matrix curMatrix = new Matrix();// 保存當前的矩陣
private PointF startPoint = new PointF();
private PointF endPoint;
private int mode = 0;
private float startdistance;
class ImageViewTouchListener implements OnTouchListener {
@Override
public boolean onTouch(View v, MotionEvent event) {
// 一隻手指情況
// 兩隻手情況 起始點和終點
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:// 單隻手指按下
curMatrix.set(matrix);
startPoint.set(event.getX(), event.getY());
mode = DRAG;
break;
case MotionEvent.ACTION_MOVE:
if (mode == DRAG) {
// 獲取結束點的座標
float dx = event.getX() - startPoint.x;
float dy = event.getY() - startPoint.y;
matrix.set(curMatrix);
matrix.postTranslate(dx, dy);// 移動到指定的位置
} else if (mode == ZOOM) {
float distance = distance(event);
if (distance > 5f) {
matrix.set(curMatrix);
float scale = distance / startdistance;
matrix.preScale(scale, scale, endPoint.x, endPoint.y);
}
}
break;
case MotionEvent.ACTION_POINTER_DOWN:// 如果一隻手指按下屏幕，後續
startdistance = distance(event);
if (startdistance > 5f) {
// 兩手指間的距離像素>5，認爲多點
mode = ZOOM;
curMatrix.set(matrix);
endPoint = getMidPoint(event);
}
break;
case MotionEvent.ACTION_UP:// 最後一隻離開屏幕觸發的事件
break;
case MotionEvent.ACTION_POINTER_UP:// 還有一隻手指沒有離開
mode = NONE;
break;
}
if (id == 0) {
layout.removeView(img);
} else {
layout.removeView(CBI_Activity.this.findViewById(id));
}
id++;
CustomomImageView imgView = new CustomomImageView(
CBI_Activity.this, matrix);
imgView.setImageMatrix(matrix);
imgView.setId(id);
imgView.setOnTouchListener(listener);
layout.addView(imgView, 2);
return true;
}
private PointF getMidPoint(MotionEvent event) {
float eX = (event.getX(1) - event.getX(0)) / 2;
float eY = (event.getY(1) - event.getY(0)) / 2;
return new PointF(eX, eY);
}
}
private float distance(MotionEvent event) {
float eX = event.getX(1) - event.getX(0);
float eY = event.getY(1) - event.getY(0);
return FloatMath.sqrt(eX * eX + eY * eY);
}
class CustomomImageView extends ImageView {
private Matrix mMatrix = new Matrix();
public CustomomImageView(Context context, Matrix mMatrix) {
super(context);
this.mMatrix = mMatrix;
}
@Override
protected void onDraw(Canvas canvas) {
// 畫出變換後的圖像
canvas.drawBitmap(bitmap, mMatrix, null);
super.onDraw(canvas);
}
}
public void big(View v) {// 標籤中添加點擊事件
Matrix matrix = new Matrix();
scaleWdith *= zoomin;
scaleHeight *= zoomin;
matrix.postScale(scaleWdith, scaleHeight);
matrix.setRotate(120);
matrix.setTranslate(300, 300);
if (id == 0) {
layout.removeView(img);
} else {
layout.removeView(this.findViewById(id));
}
id++;
CustomomImageView imgView = new CustomomImageView(this, matrix);
imgView.setImageMatrix(matrix);
imgView.setId(id);
layout.addView(imgView, 2);
// setContentView(layout);
Toast.makeText(CBI_Activity.this, "執行了", Toast.LENGTH_SHORT).show();
}
}