如何处理这个线程？
如何处理这个线程？
提问于 2011-11-10 17:30:56
在我的应用程序中，当活动A被调用时，有一个线程正在运行。现在，我将转到另一个活动B，但不对该线程执行任何操作。还有关于活动B的另一个线程。现在，在完成活动B的活动之后，我返回到活动A。
当时我得到了一个错误，活动A上的线程已经在运行了。那么，我应该做些什么来处理这个错误呢？每次当我从活动B返回到A时，我的应用程序崩溃。
谢谢。
在这个错误日志绘图图面中是我的活动A，如上所述。错误日志：
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): FATAL EXCEPTION: main
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): java.lang.IllegalThreadStateException: Thread already started.
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at java.lang.Thread.start(Thread.java:1322)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at com.example.drawing.DrawingSurface.surfaceCreated(DrawingSurface.java:113)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at android.view.SurfaceView.updateWindow(SurfaceView.java:532)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at android.view.SurfaceView.onWindowVisibilityChanged(SurfaceView.java:206)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at android.view.View.dispatchWindowVisibilityChanged(View.java:3891)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:719)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:719)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:719)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at android.view.ViewGroup.dispatchWindowVisibilityChanged(ViewGroup.java:719)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at android.view.ViewRoot.performTraversals(ViewRoot.java:744)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at android.view.ViewRoot.handleMessage(ViewRoot.java:1727)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at android.os.Handler.dispatchMessage(Handler.java:99)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at android.os.Looper.loop(Looper.java:123)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at android.app.ActivityThread.main(ActivityThread.java:4627)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at java.lang.reflect.Method.invokeNative(Native Method)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at java.lang.reflect.Method.invoke(Method.java:521)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
11-10 15:08:24.730: ERROR/AndroidRuntime(1145): at dalvik.system.NativeStart.main(Native Method)我遇到错误的DrawingSurface类：
public class DrawingSurface extends SurfaceView implements SurfaceHolder.Callback {
private Boolean _run;
protected DrawThread thread;
public Canvas canvas = null;
private CommandManager commandManager;
//private Bitmap myBitmap;
private Bitmap mBitmap;
public DrawingSurface(Context context, AttributeSet attrs) {
super(context, attrs);
getHolder().addCallback(this);
commandManager = new CommandManager();
thread = new DrawThread(getHolder());
}
class DrawThread extends Thread{
private SurfaceHolder mSurfaceHolder;
public DrawThread(SurfaceHolder surfaceHolder){
mSurfaceHolder = surfaceHolder;
}
public void setRunning(boolean run) {
_run = run;
}
@Override
public void run() {
//Canvas canvas = null;
while (_run){
try{
canvas = mSurfaceHolder.lockCanvas(null);
if(mBitmap == null){
mBitmap = Bitmap.createBitmap (1, 1, Bitmap.Config.ARGB_8888);
}
final Canvas c = new Canvas (mBitmap);
//canvas.drawColor(0, PorterDuff.Mode.CLEAR);
c.drawColor(0, PorterDuff.Mode.CLEAR);
canvas.drawColor(Color.WHITE);
// Bitmap kangoo = BitmapFactory.decodeResource(getResources(),R.drawable.icon);
if(!(DrawingActivity.imagePath==null)){
c.drawBitmap(DrawingActivity.mBitmap, 0, 0, null);
}
commandManager.executeAll(c);
canvas.drawBitmap (mBitmap, 0, 0,null);
} finally {
mSurfaceHolder.unlockCanvasAndPost(canvas);
}
}
}
}
public void addDrawingPath (DrawingPath drawingPath){
commandManager.addCommand(drawingPath);
}
public boolean hasMoreRedo(){
return commandManager.hasMoreRedo();
}
public void redo(){
commandManager.redo();
}
public void undo(){
commandManager.undo();
}
public boolean hasMoreUndo(){
return commandManager.hasMoreRedo();
}
public Bitmap getBitmap(){
return mBitmap;
}
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
// TODO Auto-generated method stub
mBitmap = Bitmap.createBitmap (width, height, Bitmap.Config.ARGB_8888);;
}
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
thread.setRunning(true);
thread.start(); // error at this line
if(!thread.isAlive())
thread.start();
}
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
boolean retry = true;
thread.setRunning(false);
while (retry) {
try {
thread.join();
retry = false;
} catch (InterruptedException e) {
// we will try it again and again...
}
}
}
}回答 2
Stack Overflow用户
回答已采纳
发布于 2011-11-10 17:49:23
如果您使用AsyncTask，它们将在您离开某个活动后自动关闭，而不是使用Thread和Runnable。
或者，如果您只想使用Thread，那么在离开该活动之前，您必须使用t.interrupt()来停止任何正在运行的Thread t。
因此，我猜将t.interrupt()放在活动的onPause()方法中以停止Thread
编辑:此行是冗余的
if(!thread.isAlive())
thread.start(); 我不明白你想要做什么，
thread.setRunning(true);这可能会产生一些问题，请删除此内容，然后重试
也就是说，试试这个
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
thread.start(); // error at this line
}Stack Overflow用户
发布于 2011-11-10 18:13:10
这将不起作用(大多数情况下是->竞争条件)：
thread.start(); // error at this line
if(!thread.isAlive()) thread.start();别干那事。一个线程只能启动一次，而且肯定有，没有理由重试启动它。
thread.start();确实是启动线程所需的全部。
编辑：
while (retry) {
thread.join();
retry = false;
}没有任何意义。只需join()，并可能将中断转发到您的thread。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/8077407
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