Question

我试试并捕获“doInBackground”，如果应用程序在“doInBackground”中执行catch方法，我不希望代码运行onPostExecute。代码如下：

public class DownloadFileAsync extends AsyncTask<String, Integer, Void> {
        @Override
        protected void onPreExecute(){
             super.onPreExecute();
     }

    @Override
    protected Void doInBackground(String... aurl) {
        try{
           //some code, jump to onPostexecute after complete
        }
        catch{
            //some code, don't do onPostExecute after complete
        }
        return null;

        }

    @Override
    protected void onProgressUpdate(Integer... progress) {          
    //some code
    }

    @Override
    protected void onPostExecute(Void unused) {
    //some code
    }
}

Answer 1

您可以尝试在cancel(true)中使用doInBackground()。请尝试以下代码：

protected Void doInBackground(String... aurl) {
    try{
       //some code, jump to onPostexecute after complete
    }
    catch{
        cancel(true);
    }
    return null;

    }

关于cancel()

的官方说明

调用此方法将导致调用onCancelled（Object）在doInBackground（Object []）返回后的UI线程上。打电话给这个方法保证永远不会调用onPostExecute（Object）。后调用此方法时，应检查返回的值 isCancelled（）定期从doInBackground（Object []）来完成尽早完成任务。

点击此链接了解更多详情：

http://developer.android.com/reference/android/os/AsyncTask.html#cancel(boolean）

Answer 2

从您的AsyncTask的doInBackground()到onPostExecute()返回布尔数据类型。并检查你想要为成功做些什么，

@Override
    protected boolean doInBackground(String... aurl) {
        try{
           //some code, jump to onPostexecute after complete

         return true;
        }
        catch{
            //some code, don't do onPostExecute after complete

        return false;
        }   
      }

和

@Override
    protected void onPostExecute(boolean flag) {
    if(flag)
     {
      //some code
     }
    }

Answer 3

您可以在AsyncTask中设置一个布尔变量并检查该变量。例如：

public class DownloadFileAsync extends AsyncTask<String, Integer, Void> {

 private boolean run_do_in_background = true;

    @Override
    protected void onPreExecute(){
         super.onPreExecute();
 }

@Override
protected Void doInBackground(String... aurl) {
    try{
       //some code, jump to onPostexecute after complete
    }
    catch{
        //some code, don't do onPostExecute after complete
        run_do_in_background = false;
    }
    return null;

    }

@Override
protected void onProgressUpdate(Integer... progress) {     

//some code
}

@Override
protected void onPostExecute(Void unused) {
 if(run_do_in_background) { //only if this is true will excecute the code in doInBackground
//some code
}
}
}

Answer 4

使用Pair，以便返回两个结果

示例，将ANYTHING替换为您要返回的类型：

public class DownloadFileAsync extends AsyncTask<String, Integer, Pair<Exception, ANYTHING> > {    
    @Override
    protected Pair<Exception, ANYTHING> doInBackground(String... aurl) {
        try{
           return new Pair<Exception, ANYTHING>(null, /* anything can go here */);

        }
        catch (Exception e) {
             return new Pair<Exception, ANYTHING>(e, null);
        }    
    }

    @Override
    protected void onPostExecute(Pair<Exception, ANYTHING> result) {
        // Evaluate the exception here
        if(result.first != null) {
            // an eror occured, do something about it
        }
    }
}

这种方式允许你处理onPostExecute中的异常，并且如果一切正常，则从result.second获取结果。

asynctask取消onpostexecute

4 个答案: