[英]How to show toast message from background thread
考虑以下代码。 在Service.onStart()
方法中,我创建并启动了一个应该显示 Toast 消息的线程,但它不起作用!
public class MyService extends Service{
private static final String TAG = "MyService";
@Override
public IBinder onBind(Intent intent)
{
return null;
}
@Override
public void onCreate()
{
Toast.makeText(this, "My Service Created", Toast.LENGTH_SHORT).show();
}
@Override
public void onDestroy()
{
Toast.makeText(this, "My Service Stopped", Toast.LENGTH_SHORT).show();
}
@Override
public void onStart(Intent intent, int startid)
{
Toast.makeText(this, "My Service Started", Toast.LENGTH_SHORT).show();
DBIteratorThread dbThread=new DBIteratorThread();
dbThread.myService=this;
Thread t1 = new Thread(dbThread);
t1.start();
}
}
class DBIteratorThread implements Runnable
{
MyService myService;
public void run()
{
// Toast.makeText(myService, "Thread is Running", Toast.LENGTH_SHORT).show();
}
}
在主/UI 线程中做 UI 的事情。 试试这个:
Handler handler = new Handler(Looper.getMainLooper());
handler.post(new Runnable() {
@Override
public void run() {
//Your UI code here
}
});
我写了一个类来显示来自后台进程的Toasts
。 可以在任何地方使用,例如在AsyncTask
。 您只需要创建此类的一个实例,例如
ToastHandler mToastHandler = new ToastHandler(yourContext);
然后调用showToast()
用文字或资源ID和Toast's
持续时间就像你通常会用makeToast()
这是代码或直接下载链接:
import android.content.Context;
import android.os.Handler;
import android.widget.Toast;
/**
* A class for showing a <code>Toast</code> from background processes using a
* <code>Handler</code>.
*
* @author kaolick
*/
public class ToastHandler
{
// General attributes
private Context mContext;
private Handler mHandler;
/**
* Class constructor.
*
* @param _context
* The <code>Context</code> for showing the <code>Toast</code>
*/
public ToastHandler(Context _context)
{
this.mContext = _context;
this.mHandler = new Handler();
}
/**
* Runs the <code>Runnable</code> in a separate <code>Thread</code>.
*
* @param _runnable
* The <code>Runnable</code> containing the <code>Toast</code>
*/
private void runRunnable(final Runnable _runnable)
{
Thread thread = new Thread()
{
public void run()
{
mHandler.post(_runnable);
}
};
thread.start();
thread.interrupt();
thread = null;
}
/**
* Shows a <code>Toast</code> using a <code>Handler</code>. Can be used in
* background processes.
*
* @param _resID
* The resource id of the string resource to use. Can be
* formatted text.
* @param _duration
* How long to display the message. Only use LENGTH_LONG or
* LENGTH_SHORT from <code>Toast</code>.
*/
public void showToast(final int _resID, final int _duration)
{
final Runnable runnable = new Runnable()
{
@Override
public void run()
{
// Get the text for the given resource ID
String text = mContext.getResources().getString(_resID);
Toast.makeText(mContext, text, _duration).show();
}
};
runRunnable(runnable);
}
/**
* Shows a <code>Toast</code> using a <code>Handler</code>. Can be used in
* background processes.
*
* @param _text
* The text to show. Can be formatted text.
* @param _duration
* How long to display the message. Only use LENGTH_LONG or
* LENGTH_SHORT from <code>Toast</code>.
*/
public void showToast(final CharSequence _text, final int _duration)
{
final Runnable runnable = new Runnable()
{
@Override
public void run()
{
Toast.makeText(mContext, _text, _duration).show();
}
};
runRunnable(runnable);
}
}
您应该能够使用 getApplicationContext() 方法来获取用于显示 Toast 的上下文。
请参阅getApplication() 与 getApplicationContext()以了解有关此问题的一些很好的讨论。
用getApplicationContext()
替换单词this
然后会出现消息
Toast.makeText(this, "My Service Created", Toast.LENGTH_SHORT).show();
正确的 :
Toast.makeText(getApplicationContext(), "My Service Created", Toast.LENGTH_SHORT).show();
您不能在不是活动的 ui 线程的线程上显示 Toast。
如果您使用runOnUiThread
方法,则只能在其他地方运行它,以便它在 ui 线程上运行
看看这个问题
Android:在线程中吐司
我们为此目的使用处理程序,因为它很容易...... :)
脚步:
它运行良好。
mhandler.post(new Runnable() {
public void run() {
Toast.makeText(context,"Run ends",Toast.LENGTH_LONG).show();
}
});
用getBaseContext()
替换this
。
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