開發(fā)環(huán)境為android4.1.
Handler使用例1
這個(gè)例子是最簡單的介紹handler使用的,是將handler綁定到它所建立的線程中.
本次實(shí)驗(yàn)完成的功能是:單擊Start按鈕，程序會(huì)開始啟動(dòng)線程，并且線程程序完成后延時(shí)1s會(huì)繼續(xù)啟動(dòng)該線程，每次線程的run函數(shù)中完成對(duì)界面輸出nUpdateThread...文字，不停的運(yùn)行下去，當(dāng)單擊End按鈕時(shí)，該線程就會(huì)停止，如果繼續(xù)單擊Start，則文字又開始輸出了。
軟件界面如下：
實(shí)驗(yàn)主要部分代碼和注釋：
MainActivity.java:
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends Activity {
private TextView text_view = null;
private Button start = null;
private Button end = null;
//使用handler時(shí)首先要?jiǎng)?chuàng)建一個(gè)handler
Handler handler = new Handler();
//要用handler來處理多線程可以使用runnable接口，這里先定義該接口
//線程中運(yùn)行該接口的run函數(shù)
Runnable update_thread = new Runnable()
{
public void run()
{
//線程每次執(zhí)行時(shí)輸出"UpdateThread..."文字,且自動(dòng)換行
//textview的append功能和Qt中的append類似，不會(huì)覆蓋前面
//的內(nèi)容，只是Qt中的append默認(rèn)是自動(dòng)換行模式
text_view.append("/nUpdateThread...");
//延時(shí)1s后又將線程加入到線程隊(duì)列中
handler.postDelayed(update_thread, 1000);
}
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
text_view = (TextView)findViewById(R.id.text_view);
start = (Button)findViewById(R.id.start);
start.setOnClickListener(new StartClickListener());
end = (Button)findViewById(R.id.end);
end.setOnClickListener(new EndClickListener());
}
private class StartClickListener implements OnClickListener
{
public void onClick(View v) {
// TODO Auto-generated method stub
//將線程接口立刻送到線程隊(duì)列中
handler.post(update_thread);
}
}
private class EndClickListener implements OnClickListener
{
public void onClick(View v) {
// TODO Auto-generated method stub
//將接口從線程隊(duì)列中移除
handler.removeCallbacks(update_thread);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
<TextView
android:id="@+id/text_view"
android:layout_width="fill_parent"
android:layout_height="200dip"
android:text="@string/hello_world"
tools:context=".MainActivity" />
<Button
android:id="@+id/start"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/start"
/>
<Button
android:id="@+id/end"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/end"
/>
</LinearLayout>
單擊Start按鈕后，更新的進(jìn)度條結(jié)果如下（怎么感覺4.1版本android進(jìn)度條那么小呢？不懂該怎么設(shè)置）：
實(shí)驗(yàn)主要部分代碼和注釋：
MainActivity.java:
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
public class MainActivity extends Activity {
private ProgressBar progress_bar = null;
private Button start = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
progress_bar = (ProgressBar)findViewById(R.id.progress_bar);
start = (Button)findViewById(R.id.start);
start.setOnClickListener(new StartOnClickListenr());
}
private class StartOnClickListenr implements OnClickListener
{
public void onClick(View v) {
// TODO Auto-generated method stub
//讓進(jìn)度條顯示出來
progress_bar.setVisibility(View.VISIBLE);
//將線程加入到handler的線程隊(duì)列中
update_progress_bar.post(update_thread);
}
}
//創(chuàng)建一個(gè)handler，內(nèi)部完成處理消息方法
Handler update_progress_bar = new Handler()
{
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
//super.handleMessage(msg);
//顯示進(jìn)度條
progress_bar.setProgress(msg.arg1);
//重新把進(jìn)程加入到進(jìn)程隊(duì)列中
update_progress_bar.post(update_thread);
}
};//不加這個(gè)分號(hào)則不能自動(dòng)添加代碼
Runnable update_thread = new Runnable()
{
int i = 0;
public void run() {
// TODO Auto-generated method stub
i += 10;
//首先獲得一個(gè)消息結(jié)構(gòu)
Message msg = update_progress_bar.obtainMessage();
//給消息結(jié)構(gòu)的arg1參數(shù)賦值
msg.arg1 = i;
//延時(shí)1s，java中的try+catch用來排錯(cuò)處理
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO: handle exception
e.printStackTrace();
}
//把消息發(fā)送到消息隊(duì)列中
update_progress_bar.sendMessage(msg);
if(i == 100)
//把線程從線程隊(duì)列中移除
update_progress_bar.removeCallbacks(update_thread);
}
};
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
<Button
android:id="@+id/start"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:text="@string/start"
/>
<ProgressBar
android:id="@+id/progress_bar"
android:layout_width="fill_parent"
android:layout_height="100dip"
android:layout_alignParentTop="true"
style="?android:attr/progressBarStyleHorizontal"
android:visibility="gone"
/>
</RelativeLayout>
MainActivity.java:
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.Menu;
public class MainActivity extends Activity {
//新建一個(gè)handler
private Handler handler = new Handler();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//將runnable加載到handler的線程隊(duì)列中去
// handler.post(r);
Thread t = new Thread(r);
t.start();
setContentView(R.layout.activity_main);
//打印activtiy線程信息
System.out.println("activity_id---->"+Thread.currentThread().getId());
System.out.println("activity_name---->"+Thread.currentThread().getName());
}
Runnable r = new Runnable()
{
public void run() {
// TODO Auto-generated method stub
//打印新建線程信息
System.out.println("handler_id---->"+Thread.currentThread().getId());
System.out.println("handler_name---->"+Thread.currentThread().getName());
//延時(shí)10s，為了觀察主界面中內(nèi)容出現(xiàn)的時(shí)間
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
// TODO: handle exception
e.printStackTrace();
}
}
};
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Looper;
import android.os.Message;
import android.view.Menu;
public class MainActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
System.out.println("activity_ID---->"+Thread.currentThread().getId());
//新建一個(gè)HanderThread對(duì)象，該對(duì)象實(shí)現(xiàn)了用Looper來處理消息隊(duì)列的功能
HandlerThread handler_thread = new HandlerThread("handler_thread");
handler_thread.start();
//MyHandler類是自己繼承的一個(gè)類，這里采用hand_thread的Looper來初始化它
MyHandler my_handler = new MyHandler(handler_thread.getLooper());
//獲得一個(gè)消息msg
Message msg = my_handler.obtainMessage();
//采用Bundle保存數(shù)據(jù)，Bundle中存放的是鍵值對(duì)的map，只是它的鍵值類型和數(shù)據(jù)類型比較固定而已
Bundle b = new Bundle();
b.putString("whether", "晴天");
b.putInt("temperature", 34);
msg.setData(b);
//將msg發(fā)送到自己的handler中，這里指的是my_handler,調(diào)用該handler的HandleMessage方法來處理該mug
msg.sendToTarget();
}
class MyHandler extends Handler
{
//空的構(gòu)造函數(shù)
public MyHandler()
{}
//以Looper類型參數(shù)傳遞的函數(shù)，Looper為消息泵，不斷循環(huán)的從消息隊(duì)列中得到消息并處理，因此
//每個(gè)消息隊(duì)列都有一個(gè)Looper，因?yàn)長ooper是已經(jīng)封裝好了的消息隊(duì)列和消息循環(huán)的類
public MyHandler(Looper looper)
{
//調(diào)用父類的構(gòu)造函數(shù)
super(looper);
}
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
System.out.println("Handler_ID---->"+Thread.currentThread().getId());
System.out.println("Handler_Name---->"+Thread.currentThread().getId());
//將消息中的bundle數(shù)據(jù)取出來
Bundle b = msg.getData();
String whether = b.getString("whether");
int temperature = b.getInt("temperature");
System.out.println("whether= "+whether+" ,temperature= "+temperature);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
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