Android开发之handler（0）

通过在非UI线程更新UI线程的错误，引出handler的使用。

package com.linxiaosheng.handler_02;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class MainActivity extends ActionBarActivity {
private TextView textView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView=(TextView)findViewById(R.id.textview);
//创建一个线程
new Thread(){
@Override
public void run() {
// TODO Auto-generated method stub
super.run();
try {
Thread.sleep(1000);
//在线程里面更新textview
textView.setText("update textview..");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}
}.start();

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}

/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {

public PlaceholderFragment() {
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}

}

报的错误：



由此可见在非UI线程更新UI线程的控件是会出错的，所以google给我们建了一个Handler类，通过handler的短信分发有更新UI线程的控件，下一节重点介绍Handler。