消息机制：
handler 主线程和其他线程的桥梁，消息队列。
handler 的handMessage()方法由主线程控制，UI的交互也在这个方法里操作；setMssage()方法由自己创建的线程调用来发送消息。他们之间通过变量Message来标识（what类成员变量）。
实例代码：
package com.android.listview;
import com.android.port.Action;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;
public class MenuActivity extends Activity {
protected static final int MSG = 0;
String[] optionMenu = { "新建", "保存", "更新" };
private Handler handler = new Handler(){
public void handleMessage(Message msg) {
if(msg.what == MSG){
Toast.makeText(MenuActivity.this, "更新完成", 1000).show();
}
};
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// TODO 自动生成的方法存根
for (int i = 0; i < optionMenu.length; i++) {
menu.add(0, i, i, optionMenu[i]);
}
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int itemId = item.getItemId();
if (itemId == 0) {
// 提示
new NewAction().execute();
} else if (itemId == 1) {
// 单选
new SaveAction().execute();
} else if (itemId == 2) {
//更新
new UpdateAction().execute();
}
return super.onOptionsItemSelected(item);
}
class NewAction implements Action {
@Override
public void execute() {
// TODO 自动生成的方法存根
// 提示
AlertDialog.Builder builder = new AlertDialog.Builder(
MenuActivity.this);
builder.setTitle("确定");
builder.setMessage("确定要新建吗？");
builder.setNegativeButton("确定", new OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
Toast.makeText(MenuActivity.this, "已经新建", 500).show();
}
});
builder.setPositiveButton("取消", new OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
Toast.makeText(MenuActivity.this, "取消新建", 500).show();
}
});
AlertDialog dialog = builder.create();
dialog.show();
}
}
class SaveAction implements Action {
int position = 0;
String[] num = new String[] { "One", "Two", "Three" };
@Override
public void execute() {
// TODO 自动生成的方法存根
//保存
AlertDialog.Builder builder = new AlertDialog.Builder(
MenuActivity.this);
builder.setTitle("单选");
builder.setSingleChoiceItems(num, 0, new OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Toast.makeText(MenuActivity.this, num[which], 500).show();
position = which;
}
});
builder.setNegativeButton("确定", new OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
Toast.makeText(MenuActivity.this, num[position] + "已经保存",
500).show();
}
});
builder.setPositiveButton("取消", new OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
Toast.makeText(MenuActivity.this, num[position] + "取消保存",
500).show();
}
});
AlertDialog dialog = builder.create();
dialog.show();
}
}
class UpdateAction implements Action {
ProgressDialog pd;
Message msg = new Message();
@Override
public void execute() {
// TODO 自动生成的方法存根
AlertDialog.Builder builder = new AlertDialog.Builder(MenuActivity.this);
builder.setTitle("更新");
builder.setItems(new String[] { "One", "Two", "Three" },
new OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// TODO 自动生成的方法存根
pd = new ProgressDialog(MenuActivity.this);
pd.setTitle("稍等片刻");
pd.setMessage("一会就好，相信我没死机~");
pd.show();
new Thread() {
@Override
public void run() {
super.run();
try {
Thread.sleep(10000);
pd.dismiss();
msg.what=MSG;
handler.sendMessage(msg);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}.start();
}
});
AlertDialog dialog = builder.create();
dialog.show();
}
}
}
谢谢~