Question

现在有一天，这是我迈向android的第一步。我只是尝试使用“下载”按钮实现进度条。当我按下下载按钮进度条继续进行但当整个进度结束时我无法隐藏进度条。这是我的代码。请帮帮我。

public class ProgressBarDemo extends Activity
{

    ProgressBar pb;
    Button bt;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.progressbar);

        pb = (ProgressBar) findViewById(R.id.progressBar1);
        bt = (Button) findViewById(R.id.button1);

        pb.setVisibility(View.VISIBLE);

        bt.setOnClickListener(new OnClickListener() 
        {

            public void onClick(View v)
            {
                Thread timer = new Thread()
                {
                    public void run()
                    {
                        try
                        {
                            for(int i=0; i<=50; i ++)
                            {   
                                pb.incrementProgressBy(i);
                                sleep(1000);
                            }

                                pb.setVisibility(View.INVISIBLE);
                                Toast.makeText(ProgressBarDemo.this, "Thank you for downloading", Toast.LENGTH_SHORT).show();

                        }catch(Exception e){}

                    }
                };
                timer.start();
            }

        });

    }

}

Answer 1

你应该只修改mainThread（UI线程）中的ui元素，试试

pb.post(new Runnable() {

        @Override
        public void run() {
            pb.setVisibility(View.INVISIBLE);
        }
    })

代替。

也许你必须使用相同的东西来增加你的进度条。 Alternativley你可以使用AsyncTask http://developer.android.com/reference/android/os/AsyncTask.html类。 onProgressUpdate和onPostExecute会自动在UIThread中调用。

Answer 2

你不应该从不同的线程做UI任务。使用这个......

public class ProgressBarDemo extends Activity
    {

        ProgressBar pb;
        Button bt;
   @Override
        protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    pb = (ProgressBar) findViewById(R.id.progressBar1);
    bt = (Button) findViewById(R.id.button1);

    pb.setVisibility(View.VISIBLE);

    bt.setOnClickListener(new OnClickListener() 
    {

        public void onClick(View v)
        {
            Thread timer = new Thread()
            {
                public void run()
                {
                    try
                    {
                        for(int i=1; i<=100; i ++)
                        {   
                            pb.setProgress(i);
                            sleep(100);
                        }


                                }catch(Exception e){}
                    finally{
                        runOnUiThread( new Runnable() {
                            public void run() {
                                 pb.setVisibility(View.INVISIBLE);
                            Toast.makeText(ProgressBarDemo .this, "Thank you for downloading", Toast.LENGTH_SHORT).show();
                            }
                        });
                    }

                }
            };
            timer.start();
        }

    });

}


    }

Answer 3

你也可以使用AsynTask这是一个更好的解决方案......

public class ProgressBarDemo extends Activity
{

    ProgressBar pb;
    Button bt;
@Override
    protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

pb = (ProgressBar) findViewById(R.id.progressBar1);
bt = (Button) findViewById(R.id.button1);

pb.setVisibility(View.VISIBLE);

bt.setOnClickListener(new OnClickListener() 
{

    public void onClick(View v)
    {
        new AsynTasks().execute();
    }
});

}

class AsynTasks extends AsyncTask<Void, Integer, Void>
{

    @Override
    protected Void doInBackground(Void... params) {
        for(int i=1;i<=100;i++)
        {
            SystemClock.sleep(1000);
             publishProgress(i);
        }
        return null;
    }
    @Override
    protected void onPostExecute(Void result) {
        super.onPostExecute(result);
          pb.setVisibility(View.INVISIBLE);
          Toast.makeText(ProgressBarDemo .this, "Thank you for downloading", Toast.LENGTH_SHORT).show();
    }
    @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);
          pb.setProgress(values[0]);
    }
}
}

带螺纹的进度条

3 个答案: