android开发获取网络图片并可拖拽移动

这一篇讲获取网络图片，然后显示出来，并对其操作，如拖拽，放大，缩小，移动。

首先，先访问网络图片，代码如下：

先定义一个线程，因为在android4.0以上的系统中，不支持有阻塞的操作在主线程里发生，所以得新定义一个线程，这个线程包括访问网络操作。

Thread xiaoli_thread=new Thread(new Runnable(){
@Override//该线程通过网络，获取校历的数据流
public void run() {
try{
URL url= new URL(PATH);
HttpURLConnection conn= (HttpURLConnection)url.openConnection();
conn.setConnectTimeout(6 * 1000); // 别超过6秒
conn.setDoInput(true);
conn.connect();
InputStream inputStream=conn.getInputStream();
if(inputStream==null){
Log.i(TAG,"picture got failed");
}else{
bmp= BitmapFactory.decodeStream(inputStream);
Log.i(TAG,"picture got");

MAX_W=bmp.getWidth()*2;
MAX_H=bmp.getHeight()*2;
MIN_W=bmp.getWidth()/2;
MIN_H=bmp.getHeight()/2;

Message msg=new Message();
msg.what=SHOW_PICTURE;
handler.sendMessage(msg);
}
}catch (SocketTimeoutException e){
Log.i(TAG,"SocketTimeoutException");
e.printStackTrace();
}
catch (MalformedURLException e){
Log.i(TAG,"MalformedURLException");
e.printStackTrace();
}catch (IOException e) {
Log.i(TAG,"IOException");
e.printStackTrace();
}
}
});

再定义一个handler获取线程发送的消息

final Handler handler=new Handler(){
@Override//接收线程发出的信息，缓冲框消失
public void handleMessage(Message msg){
switch(msg.what){
case SHOW_PICTURE:
img.setImageBitmap(bmp);
dialog.dismiss();
break;
}
}
};

然后，在oncreate()方法中

//后台启动校历线程,加载学校校历图片
xiaoli_thread.start();
Log.i(TAG,"new xiaoli_thread start!");

这样网络上的图片就可以显示出来了，当然还要有配置文件，这里就不说了。



接下来，就是对图片的操作。

先定义触摸、放大、缩小事件

img.setOnTouchListener(new MulitPointTouchListener(img));

zoomcon=(ZoomControls)super.findViewById(R.id.zoomcontrol);
this.zoomcon.setOnZoomInClickListener(new onzoominclicklistener());//放大监听
this.zoomcon.setOnZoomOutClickListener(new onzoomoutclicklistener());//缩小监听
zoomcon.setIsZoomInEnabled(true);
zoomcon.setIsZoomOutEnabled(true);

然后，再写具体的方法

1、触摸即多点触控方法

/**
* @继承OnTouchListener实现多点触控
*/
public class MulitPointTouchListener implements OnTouchListener {
Matrix matrix = new Matrix();
Matrix savedMatrix = new Matrix();

public ImageView image;
static final int NONE = 0;
static final int DRAG = 1; //拖拽
static final int ZOOM = 2; //缩放
int mode = NONE;

PointF start = new PointF();
PointF mid = new PointF();
float oldDist = 1f;

public MulitPointTouchListener(ImageView image) {
super();
this.image = image;
}

@Override
public boolean onTouch(View v, MotionEvent event) {
this.image.setScaleType(ScaleType.MATRIX);
ImageView view = (ImageView) v;
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
Log.w("FLAG", "ACTION_DOWN");

//设置底部组件的可见性
if(IsVisible){
bottom.setVisibility(View.INVISIBLE);
IsVisible = false;
Log.i(TAG,"onClick1");
}else{
bottom.setVisibility(View.VISIBLE);
IsVisible = true;
Log.i(TAG,"onClick2");
}

matrix.set(view.getImageMatrix());
savedMatrix.set(matrix);
start.set(event.getX(), event.getY());
mode = DRAG;
break;
case MotionEvent.ACTION_POINTER_DOWN:
Log.w("FLAG", "ACTION_POINTER_DOWN");
oldDist = spacing(event);
if (oldDist > 10f) {
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
}
break;
case MotionEvent.ACTION_UP:
Log.w("FLAG", "ACTION_UP");
case MotionEvent.ACTION_POINTER_UP:
Log.w("FLAG", "ACTION_POINTER_UP");
mode = NONE;
break;
case MotionEvent.ACTION_MOVE:
Log.w("FLAG", "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);
}
}
break;
}
view.setImageMatrix(matrix);
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);
}

｝

2、放大操作

/**
* @放大图片
*/
private class onzoominclicklistener implements OnClickListener{
@Override
public void onClick(View v) {
int bmpWidth = bmp.getWidth();
int bmpHeight = bmp.getHeight();
//设置图片放大但比例
double scale = 1.25;
//计算这次要放大的比例
scaleWidth = (float)(scaleWidth*scale);
scaleHeight = (float)(scaleHeight*scale);
//产生新的大小但Bitmap对象
Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
try{
Bitmap resizeBmp = Bitmap.createBitmap(bmp,0,0,bmpWidth,bmpHeight,matrix,true);
if(resizeBmp.getWidth()>=(MAX_W-350 )|| resizeBmp.getHeight()>=(MAX_H-350)){
zoomcon.setIsZoomInEnabled(false);
}else{
img.setImageBitmap(resizeBmp);
zoomcon.setIsZoomOutEnabled(true);
}
}catch(IllegalArgumentException e){
Log.e(TAG,"IllegalArgumentException");
e.printStackTrace();
}catch(Exception e){
Log.e(TAG,"Exception");
e.printStackTrace();
}
}
}

3、缩小操作

/**
* @缩小图片
*/
private class onzoomoutclicklistener implements OnClickListener{
@Override
public void onClick(View v) {
int bmpWidth=bmp.getWidth();
int bmpHeight=bmp.getHeight();

/* 设置图片缩小的比例 */
double scale=0.8;
/* 计算出这次要缩小的比例 */
scaleWidth=(float) (scaleWidth*scale);
scaleHeight=(float) (scaleHeight*scale);
/* 产生reSize后的Bitmap对象 */
Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
try{
Bitmap resizeBmp = Bitmap.createBitmap(bmp,0,0,bmpWidth, bmpHeight,matrix,true);
if(resizeBmp.getWidth()<=MIN_W || resizeBmp.getHeight()<=MIN_H){
zoomcon.setIsZoomOutEnabled(false);
}else{
img.setImageBitmap(resizeBmp);
zoomcon.setIsZoomInEnabled(true);
}
}catch(IllegalArgumentException e){
Log.e(TAG,"IllegalArgumentException");
e.printStackTrace();
}catch(Exception e){
Log.e(TAG,"Exception");
e.printStackTrace();
}

}
}

啊，代码有点长，最好在最后还要加上回收图片，因为它占的内存比较多

@Override
protected void onStop() {
if(bmp!=null){
if(!bmp.isRecycled()){
bmp.recycle();   //回收图片所占的内存
bmp=null;
System.gc();  //提醒系统及时回收
}
}
super.onStop();
}

@Override
protected void onDestroy() {
super.onDestroy();
if(bmp!=null){
if(!bmp.isRecycled()){
bmp.recycle();   //回收图片所占的内存
bmp=null;
System.gc();  //提醒系统及时回收
}
}
}

效果图如下：





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