直接在UI線(xiàn)程中開(kāi)啟子線(xiàn)程來(lái)更新TextView顯示的內(nèi)容，運(yùn)行程序我們會(huì)發(fā)現(xiàn)，如下錯(cuò) 誤：android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.翻譯過(guò)來(lái)就是：只有創(chuàng)建這個(gè)控件的線(xiàn)程才能去更新該控件的內(nèi)容。

所有的UI線(xiàn)程要去負(fù)責(zé)View的創(chuàng)建并且維護(hù)它，例如更新冒個(gè)TextView的顯示，都必須在主線(xiàn)程中去做，我們不能直接在UI線(xiàn)程中去創(chuàng)建子線(xiàn)程，要利用消息機(jī)制：handler，如下就是handler的簡(jiǎn)單工作原理圖：

既然android給我們提供了Handler機(jī)制來(lái)解決這樣的問(wèn)題，請(qǐng)看如下代碼：

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

public class HandlerTestActivity?extends Activity { ????private TextView tv; ????private static final int UPDATE =?0; ????private Handler handler =?new Handler() { ????????@Override ????????public void handleMessage(Message msg) { ????????????// TODO 接收消息并且去更新UI線(xiàn)程上的控件內(nèi)容 ????????????if (msg.what == UPDATE) { ????????????????// Bundle b = msg.getData(); ????????????????// tv.setText(b.getString("num")); ????????????????tv.setText(String.valueOf(msg.obj)); ????????????} ????????????super.handleMessage(msg); ????????} ????}; ????/** Called when the activity is first created. */ ????@Override ????public void onCreate(Bundle savedInstanceState) { ????????super.onCreate(savedInstanceState); ????????setContentView(R.layout.main); ????????tv = (TextView) findViewById(R.id.tv); ????????new Thread() { ????????????@Override ????????????public void run() { ????????????????// TODO 子線(xiàn)程中通過(guò)handler發(fā)送消息給handler接收，由handler去更新TextView的值 ????????????????try { ????????????????????for (int i =?0; i <?100; i++) { ????????????????????????Thread.sleep(500); ????????????????????????Message msg =?new Message(); ????????????????????????msg.what = UPDATE; ????????????????????????// Bundle b = new Bundle(); ????????????????????????// b.putString("num", "更新后的值：" + i); ????????????????????????// msg.setData(b); ????????????????????????msg.obj =?"更新后的值：" + i; ????????????????????????handler.sendMessage(msg); ????????????????????} ????????????????}?catch (InterruptedException e) { ????????????????????e.printStackTrace(); ????????????????} ????????????} ????????}.start(); ????} }

????????我們就通過(guò)Handler機(jī)制來(lái)處理了子線(xiàn)程去更新UI線(xiàn)程控件問(wèn)題，Andrid開(kāi)發(fā)中要經(jīng)常用到這種機(jī)制。

轉(zhuǎn)載于:https://www.cnblogs.com/pinksnow520/p/4101032.html

總結(jié)

以上是生活随笔為你收集整理的Android中的Handler机制的全部?jī)?nèi)容，希望文章能夠幫你解決所遇到的問(wèn)題。

如果覺(jué)得生活随笔網(wǎng)站內(nèi)容還不錯(cuò)，歡迎將生活随笔推薦給好友。