blocks|key|997884|text|就像this或this一样，都有一个显示Toast的Runnable。也就是说，|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|997885|Activity+activity+=+//+reference+to+an+Activity
//+or
View+view+=+//+reference+to+a+View

activity.runOnUiThread(new+Runnable()+{
++++@Override
++++public+void+run()+{
++++++++showToast(activity);
++++}
});
//+or
view.post(new+Runnable()+{
++++@Override
++++public+void+run()+{
++++++++showToast(view.getContext());
++++}
});

private+void+showToast(Context+ctx)+{
++++Toast.makeText(ctx,+"Hi!",+Toast.LENGTH_SHORT).show();
}|code-block|syntax|javascript|997886|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/reference/android/app/Activity.html#runOnUiThread(java.lang.Runnable)|1|http://developer.android.com/reference/android/view/View.html#post(java.lang.Runnable))^0|K|5|Q|8|2|4|0|7|4|1|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]|$9|12|A|13|1|14]]|E|$]]|$1|F|3|G|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]|S|$5|N|O|P|E|$Q|T]]]]

Like <a href="http://developer.android.com/reference/android/app/Activity.html#runOnUiThread(java.lang.Runnable)" rel="noreferrer">this</a> or <a href="http://developer.android.com/reference/android/view/View.html#post(java.lang.Runnable)" rel="noreferrer">this</a>, with a <code>Runnable</code> that shows the <code>Toast</code>.
Namely,

<pre><code>Activity activity = // reference to an Activity
// or
View view = // reference to a View

activity.runOnUiThread(new Runnable() {
 @Override
 public void run() {
 showToast(activity);
 }
});
// or
view.post(new Runnable() {
 @Override
 public void run() {
 showToast(view.getContext());
 }
});

private void showToast(Context ctx) {
 Toast.makeText(ctx, "Hi!", Toast.LENGTH_SHORT).show();
}
</code></pre>

blocks|key|1212180|text|你可以通过从你的线程中调用Activity的runOnUiThread方法来实现：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1212181|activity.runOnUiThread(new+Runnable()+{
++++public+void+run()+{
++++++++Toast.makeText(activity,+"Hello",+Toast.LENGTH_SHORT).show();
++++}
});|code-block|syntax|javascript|1212182|entityMap^0|D|8|M|D|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

You can do it by calling an <code>Activity</code>'s <code>runOnUiThread</code> method from your thread:

<pre><code>activity.runOnUiThread(new Runnable() {
 public void run() {
 Toast.makeText(activity, "Hello", Toast.LENGTH_SHORT).show();
 }
});
</code></pre>

blocks|key|1212209|text|我喜欢在我的活动中有一个名为showToast的方法，我可以从任何地方调用它……|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1212210|public+void+showToast(final+String+toast)
{
++++runOnUiThread(()+->+Toast.makeText(MyActivity.this,+toast,+Toast.LENGTH_SHORT).show());
}|code-block|syntax|javascript|1212211|然后，我最常在任何线程的MyActivity中调用它，就像这样……|1212212|showToast(getString(R.string.MyMessage));|1212213|entityMap^0|E|9|0|0|C|A|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|P|$]]

I like to have a method in my activity called <code>showToast</code> which I can call from anywhere...

<pre><code>public void showToast(final String toast)
{
 runOnUiThread(() -&gt; Toast.makeText(MyActivity.this, toast, Toast.LENGTH_SHORT).show());
}
</code></pre>

I then most frequently call it from within <code>MyActivity</code> on any thread like this...

<pre><code>showToast(getString(R.string.MyMessage));
</code></pre>

blocks|key|1212257|text|您可以使用Looper发送Toast消息。请通过此+link了解更多详细信息。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1212258|public+void+showToastInThread(final+Context+context,final+String+str){
++++Looper.prepare();
++++MessageQueue+queue+=+Looper.myQueue();
++++queue.addIdleHandler(new+IdleHandler()+{
+++++++++int+mReqCount+=+0;

+++++++++@Override
+++++++++public+boolean+queueIdle()+{
+++++++++++++if+(%2B%2BmReqCount+==+2)+{
++++++++++++++++++Looper.myLooper().quit();
++++++++++++++++++return+false;
+++++++++++++}+else
++++++++++++++++++return+true;
+++++++++}
++++});
++++Toast.makeText(context,+str,Toast.LENGTH_LONG).show();++++++
++++Looper.loop();
}|code-block|syntax|javascript|1212259|它在你的线程中被调用。上下文可能是从你必须展示吐司的Activity中获得的。|1212260|entityMap|0|LINK|mutability|MUTABLE|url|http://prasanta-paul.blogspot.kr/2013/09/android-looper-and-toast-from.html^0|5|6|D|5|P|5|0|0|0|Q|8|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|F|3|G|5|H|7|12|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|13|8|@$9|14|A|15|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

You can use <code>Looper</code> to send <code>Toast</code> message. Go through this <a href="http://prasanta-paul.blogspot.kr/2013/09/android-looper-and-toast-from.html" rel="nofollow noreferrer"> link</a> for more details. 

<pre><code>public void showToastInThread(final Context context,final String str){
 Looper.prepare();
 MessageQueue queue = Looper.myQueue();
 queue.addIdleHandler(new IdleHandler() {
 int mReqCount = 0;

 @Override
 public boolean queueIdle() {
 if (++mReqCount == 2) {
 Looper.myLooper().quit();
 return false;
 } else
 return true;
 }
 });
 Toast.makeText(context, str,Toast.LENGTH_LONG).show(); 
 Looper.loop();
}
</code></pre>

and it is called in your thread. Context may be <code>Activity.getContext()</code> getting from the <code>Activity</code> you have to show the toast.

blocks|key|1212314|text|这与其他答案类似，但是针对新的可用apis进行了更新，并且更加简洁。此外，也不会假设您处于活动上下文中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1212315|public+class+MyService+extends+AnyContextSubclass+{

++++public+void+postToastMessage(final+String+message)+{
++++++++Handler+handler+=+new+Handler(Looper.getMainLooper());

++++++++handler.post(new+Runnable()+{

++++++++++++@Override
++++++++++++public+void+run()+{
++++++++++++++++Toast.makeText(getContext(),+message,+Toast.LENGTH_LONG).show();
++++++++++++}
++++++++});
++++}
}|code-block|syntax|javascript|1212316|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This is similar to other answers, however updated for new available apis and much cleaner. Also, does not assume you're in an Activity Context.

<pre><code>public class MyService extends AnyContextSubclass {

 public void postToastMessage(final String message) {
 Handler handler = new Handler(Looper.getMainLooper());

 handler.post(new Runnable() {

 @Override
 public void run() {
 Toast.makeText(getContext(), message, Toast.LENGTH_LONG).show();
 }
 });
 }
}
</code></pre>

blocks|key|998112|text|一种几乎可以在任何地方工作的方法，包括没有Activity或View的地方，就是抓取一个指向主线程的Handler并显示toast：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|998113|public+void+toast(final+Context+context,+final+String+text)+{
++Handler+handler+=+new+Handler(Looper.getMainLooper());
++handler.post(new+Runnable()+{
++++public+void+run()+{
++++++Toast.makeText(context,+text,+Toast.LENGTH_LONG).show();
++++}
++});
}|code-block|syntax|javascript|998114|这种方法的优点是它可以与任何Context一起使用，包括Service和Application。|998115|entityMap^0|L|8|U|4|1E|7|0|0|E|7|S|7|10|B|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|N|$]]

One approach that works from pretty much anywhere, including from places where you don't have an <code>Activity</code> or <code>View</code>, is to grab a <code>Handler</code> to the main thread and show the toast:
<pre><code>public void toast(final Context context, final String text) {
 Handler handler = new Handler(Looper.getMainLooper());
 handler.post(new Runnable() {
 public void run() {
 Toast.makeText(context, text, Toast.LENGTH_LONG).show();
 }
 });
}
</code></pre>
The advantage of this approach is that it works with any <code>Context</code>, including <code>Service</code> and <code>Application</code>.

blocks|key|998126|text|我基于mjaggard的回答提出了这种方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|998127|public+static+void+toastAnywhere(final+String+text)+{
++++Handler+handler+=+new+Handler(Looper.getMainLooper());
++++handler.post(new+Runnable()+{
++++++++public+void+run()+{
++++++++++++Toast.makeText(SuperApplication.getInstance().getApplicationContext(),+text,+
++++++++++++++++++++Toast.LENGTH_LONG).show();
++++++++}
++++});
}|code-block|syntax|javascript|998128|对我来说效果很好。|998129|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I made this approach based on mjaggard answer:

<pre><code>public static void toastAnywhere(final String text) {
 Handler handler = new Handler(Looper.getMainLooper());
 handler.post(new Runnable() {
 public void run() {
 Toast.makeText(SuperApplication.getInstance().getApplicationContext(), text, 
 Toast.LENGTH_LONG).show();
 }
 });
}
</code></pre>

Worked well for me.

blocks|key|998180|text|我遇到了同样的问题：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|998181|E/AndroidRuntime:+FATAL+EXCEPTION:+Thread-4
++++++++++++++Process:+com.example.languoguang.welcomeapp,+PID:+4724
++++++++++++++java.lang.RuntimeException:+Can't+toast+on+a+thread+that+has+not+called+Looper.prepare()
++++++++++++++++++at+android.widget.Toast$TN.<init>(Toast.java:393)
++++++++++++++++++at+android.widget.Toast.<init>(Toast.java:117)
++++++++++++++++++at+android.widget.Toast.makeText(Toast.java:280)
++++++++++++++++++at+android.widget.Toast.makeText(Toast.java:270)
++++++++++++++++++at+com.example.languoguang.welcomeapp.MainActivity$1.run(MainActivity.java:51)
++++++++++++++++++at+java.lang.Thread.run(Thread.java:764)
I/Process:+Sending+signal.+PID:+4724+SIG:+9
Application+terminated.|code-block|syntax|javascript|998182|之前:+onCreate函数|998183|Thread+thread+=+new+Thread(new+Runnable()+{
++++@Override
++++public+void+run()+{
++++++++Toast.makeText(getBaseContext(),+"Thread",+Toast.LENGTH_LONG).show();
++++}
});
thread.start();|998184|After:+onCreate函数|998185|runOnUiThread(new+Runnable()+{
++++@Override
++++public+void+run()+{
++++++++Toast.makeText(getBaseContext(),+"Thread",+Toast.LENGTH_LONG).show();
++++}
});|998186|啊，真灵。|998187|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

I encountered the same problem：

<pre><code>E/AndroidRuntime: FATAL EXCEPTION: Thread-4
 Process: com.example.languoguang.welcomeapp, PID: 4724
 java.lang.RuntimeException: Can't toast on a thread that has not called Looper.prepare()
 at android.widget.Toast$TN.&lt;init&gt;(Toast.java:393)
 at android.widget.Toast.&lt;init&gt;(Toast.java:117)
 at android.widget.Toast.makeText(Toast.java:280)
 at android.widget.Toast.makeText(Toast.java:270)
 at com.example.languoguang.welcomeapp.MainActivity$1.run(MainActivity.java:51)
 at java.lang.Thread.run(Thread.java:764)
I/Process: Sending signal. PID: 4724 SIG: 9
Application terminated.
</code></pre>

Before: onCreate function

<pre><code>Thread thread = new Thread(new Runnable() {
 @Override
 public void run() {
 Toast.makeText(getBaseContext(), "Thread", Toast.LENGTH_LONG).show();
 }
});
thread.start();
</code></pre>

After: onCreate function

<pre><code>runOnUiThread(new Runnable() {
 @Override
 public void run() {
 Toast.makeText(getBaseContext(), "Thread", Toast.LENGTH_LONG).show();
 }
});
</code></pre>

it worked.

blocks|key|1212499|text|java+11：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1212500|var+handler+=+new+Handler(Looper.getMainLooper);
handler.post(()+->+Toast.makeText(your_context,+"Hi!",+Toast.LENGTH_SHORT).show());|code-block|syntax|javascript|1212501|但是，Lambdas在java8中是可用的。var是在Java11中引入的。|offset|length|style|CODE|1212502|entityMap^0|0|0|M|3|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

java 11:
<pre><code>var handler = new Handler(Looper.getMainLooper);
handler.post(() -&gt; Toast.makeText(your_context, &quot;Hi!&quot;, Toast.LENGTH_SHORT).show());
</code></pre>
Lambdas are available in java 8 though. <code>var</code> is introduced in java 11.

How can I display <a href="http://developer.android.com/guide/topics/ui/notifiers/toasts.html" rel="noreferrer">Toast</a> messages from a thread?

问如何在Android上显示后台线程中的Toast？
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