主線程的職責是創建、顯示和更新UI控件、處理UI事件、啓動子線程、停止子線程;子線程的職責是進行處理和向主線程發出更新UI消息，而不是直接更新UI。
android 多線程編程報錯：
05-14 15:29:50.908: E/AndroidRuntime(2098): android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
不能在子線程直接更新ui
解決辦法：
通過handler消息機制實現ui的刷新
（1）主線程:
handler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case 0:
LoadList(getApplicationContext());
}
}
};
(2)子線程：
new Thread() {
@Override
public void run() {
Message msg = new Message();
msg.what = 0;
handler.sendMessage(msg);
Log.d("listview", "loadlist");
}
}.start();