Android中更新UI的两种方法

爱被打了一巴掌 2022-05-19 04:10 513阅读 0赞

在Android开发过程中，常需要更新界面的UI。而更新UI是要主线程来更新的，即UI线程更新。如果在主线线程之外的线程中直接更新页面 显示常会报错。抛出异常：android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

只有原始创建这个视图层次(view hierachy)的线程才能修改它的视图(view)

话不多说，贴出下面的代码

方法一：

在Activity.onCreate(Bundle savedInstanceState)中创建一个Handler类的实例， 在这个Handler实例的handleMessage回调函数中调用更新界面显示的函数。

界面：

![232431H94-0.jpg][]

1.  public class MainActivity extends Activity \{
2.  private EditText UITxt;
3.  private Button updateUIBtn;
4.  private UIHandler UIhandler;
5.  
6.  @Override
7.  public void onCreate(Bundle savedInstanceState) \{
8.  super.onCreate(savedInstanceState);
9.  setContentView(R.layout.activity\_main);
10. UITxt = (EditText)findViewById(R.id.ui\_txt);
11. updateUIBtn = (Button)findViewById(R.id.update\_ui\_btn);
12. updateUIBtn.setOnClickListener(new View.OnClickListener() \{
13. 
14. public void onClick(View v) \{
15. // TODO Auto-generated method stub
16. UIhandler = new UIHandler();
17. UIThread thread = new UIThread();
18. thread.start();
19. \}
20. \});
21. \}
22. 
23. @Override
24. public boolean onCreateOptionsMenu(Menu menu) \{
25. getMenuInflater().inflate(R.menu.activity\_main, menu);
26. return true;
27. \}
28. private class UIHandler extends Handler\{
29. @Override
30. public void handleMessage(Message msg) \{
31. // TODO Auto-generated method stub
32. super.handleMessage(msg);
33. Bundle bundle = msg.getData();
34. String color = bundle.getString("color");
35. UITxt.setText(color);
36. \}
37. \}
38. private class UIThread extends Thread\{
39. @Override
40. public void run() \{
41. try \{
42. Thread.sleep(3000);
43. \} catch (InterruptedException e) \{
44. // TODO Auto-generated catch block
45. e.printStackTrace();
46. \}
47. Message msg = new Message();
48. Bundle bundle = new Bundle();
49. bundle.putString("color", "黄色");
50. msg.setData(bundle);
51. MainActivity.this.UIhandler.sendMessage(msg);
52. 
53. \}
54. \}
55. \}

更新后：

![2324316296-1.jpg][]

方法二：利用Activity.runOnUiThread(Runnable)把更新ui的代码创建在Runnable中，然后在需要更新 ui时，把这个Runnable对象传给Activity.runOnUiThread(Runnable)。 这样Runnable对像就能在ui程序中被调用。如果当前线程是UI线程,那么行动是立即执行。如果当前线程不是UI线程,操作是发布到事件队列的UI 线程

1.  FusionField.currentActivity.runOnUiThread(new Runnable()
2.  \{
3.  public void run()
4.  \{
5.  Toast.makeText(getApplicationContext(), , "Update My UI",
6.  Toast.LENGTH\_LONG).show();
7.  \}
8.  
9.  \});

[232431H94-0.jpg]: /images/20220519/fc3753143fd847d0b1b8cdf606a5c11d.png
[2324316296-1.jpg]: /images/20220519/0dafe4fbce1a433d8fa981969baca623.png