android线程

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与ui相关的代码都是运行在主线程Main Thread中
其他的线程Worker Thread

原则上：
在安卓系统中 ui线程之外(Worker Thread)是不能修改ui的

特例：ProgressBar progressBar的成员方法等等
progressBar.setProgress();

在一个应用程序中主线程通常用于接受用户的输入以及将运算的结果反馈给用户所以主线程不能进入阻塞的状态不然无法交互
ANR:application not responding
对于一些可能造成阻塞的操作必须放在Worker Thread中执行

<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">    <ProgressBar        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:id="@+id/progressBarId"        style ="?android:attr/progressBarStyleHorizontal"/>    <Button        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:id="@+id/buttonId"        android:layout_below="@+id/progressBarId"        android:text="Button"        android:gravity="center"/></RelativeLayout>

package practice.labyrinth7x.bupt.edu.thread;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.widget.Button;import android.widget.ProgressBar;public class MainActivity extends AppCompatActivity {    private Button button;    private ProgressBar progressBar;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        button = (Button)findViewById(R.id.buttonId);        progressBar = (ProgressBar)findViewById(R.id.progressBarId);        ButtonListener buttonListener = new ButtonListener();        button.setOnClickListener(buttonListener);    }    class ButtonListener implements View.OnClickListener{        @Override        public void onClick(View v) {            MyThread myThread = new MyThread();            myThread.start();        }    }    class MyThread extends Thread{        @Override        public void run(){            for(int i =0;i < 100;i++){                try {                    Thread.sleep(2* 1000);                } catch (InterruptedException e) {                    e.printStackTrace();                }                progressBar.setProgress(progressBar.getProgress() + 1);            }        }    }    @Override    public boolean onCreateOptionsMenu(Menu menu) {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.menu_main, menu);        return true;    }    @Override    public boolean onOptionsItemSelected(MenuItem item) {        // Handle action bar item clicks here. The action bar will        // automatically handle clicks on the Home/Up button, so long        // as you specify a parent activity in AndroidManifest.xml.        int id = item.getItemId();        //noinspection SimplifiableIfStatement        if (id == R.id.action_settings) {            return true;        }        return super.onOptionsItemSelected(item);    }}

上述代码能执行
如果将控件改为TextView对象在MyThread myThread中调用setText()修改文本最后程序无法运行

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