Android的UI也是线程不安全的。也就是说,如果想要更新应用程序里的ui元素,则必须在主线程中进行。
1.布格文件:activity_main.xml
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout android:id="@+id/activity_main" xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="com.sh.androidthreadtest.MainActivity"> <Button android:id="@+id/change_text" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Change Text" /> <TextView android:id="@+id/text" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerInParent="true" android:textSize="20sp" android:text="Hello World!"/> </RelativeLayout>
2.主文件:MainActivity.java
public class MainActivity extends AppCompatActivity implements View.OnClickListener { public static final int UPDATE_TEXT =1 ; //定义一个整数常量update_text,用于表示更新textview这个动作 private TextView text; private Handler handler = new Handler(){ //新增一个handler对象,并重写父类的handlermessage()的方法并对message进行处理 @Override public void handleMessage(Message msg) { switch (msg.what){ case UPDATE_TEXT: //在这里可以进行ui操作 text.setText("Nice to meet you"); break; } } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Button changeText=(Button)findViewById(R.id.change_text); text = (TextView)findViewById(R.id.text); changeText.setOnClickListener(this); } @Override public void onClick(View v) { switch (v.getId()){ case R.id.change_text: new Thread(new Runnable() { @Override public void run() { Message message = new Message(); message.what = UPDATE_TEXT; handler.sendMessage(message);//将message对象发送出去 } }).start(); break; default: break; } } /* @Override public void onClick(View v) { switch (v.getId()){ case R.id.change_text: new Thread(new Runnable() { //从接口runnable中定义子线程 @Override public void run() { text.setText("Nice to meet you"); } }).start(); break; default: break; } }*/ }