【Android 併發程式設計】執行緒間通訊的三種基本方式，android執行緒
1. 使用管道流Pipes
“管道”是java.io包的一部分。它是Java的特性，而不是Android特有的。一條“管道”為兩個執行緒建立一個單向的通道。生產者負責寫資料，消費者負責讀取資料。
下面是一個使用管道流進行通訊的例子。
public class PipeExampleActivity extends Activity {
private static final String TAG = "PipeExampleActivity";
private EditText editText;
PipedReader r;
PipedWriter w;
private Thread workerThread;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
r = new PipedReader();
w = new PipedWriter();
try {
w.connect(r);
} catch (IOException e) {
e.printStackTrace();
}
setContentView(R.layout.activity_pipe);
editText = (EditText) findViewById(R.id.edit_text);
editText.addTextChangedListener(new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence charSequence, int start, int count, int after) {
}
@Override
public void onTextChanged(CharSequence charSequence, int start, int before, int count) {
try {
if(count > before) {
w.write(charSequence.subSequence(before, count).toString());
}
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void afterTextChanged(Editable editable) {
}
});
workerThread = new Thread(new TextHandlerTask(r));
workerThread.start();
}
@Override
protected void onDestroy() {
super.onDestroy();
workerThread.interrupt();
try {
r.close();
w.close();
} catch (IOException e) {
}
}
private static class TextHandlerTask implements Runnable {
private final PipedReader reader;
public TextHandlerTask(PipedReader reader){
this.reader = reader;
}
@Override
public void run() {
while(!Thread.currentThread().isInterrupted()){
try {
int i;
while((i = reader.read()) != -1){
char c = (char) i;
Log.d(TAG, "char = " + c);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
在這個例子中，對EditText設定一個TextWatcher監聽，一旦EditText的內容發生改變，就向“管道”中輸入字元，它就是所謂的生產者。同時，有一個工作執行緒負責從管道中讀取字元，它就是所謂的消費者。這樣，就實現了UI執行緒和工作執行緒之間的資料通訊。
2. 共享記憶體
多個執行緒共享同一份記憶體，就是說，一個變數可以同時被多個執行緒所訪問。這裡要特別注意同步和原子操作的問題。
Java中最基本的同步例子。
synchronized(this) {
while(isConditionFullfilled == false) {
wait();
}
notify();
}public class ConsumerProducer {
private final int LIMIT = 10;
private BlockingQueue<Integer> blockingQueue = new LinkedBlockingQueue<Integer>(LIMIT);
public void produce() throws InterruptedException {
int value = 0;
while (true) {
blockingQueue.put(value++);
}
}
public void consume() throws InterruptedException {
while (true) {
int value = blockingQueue.take();
}
}
}3. 使用Hander和Message
Handler的機制網上有很多教程，對其不太清楚的同學可以Google一下。
我做一下簡略的總結。
一個執行緒對應一個Looper，一個Looper持有一個MessageQueue，一個Looper可以與多個Handler繫結，一個MessageQueue中可以包含多個Message。
下面是一個使用Handler的例子。
public class HandlerExampleActivity extends Activity {
private final static int SHOW_PROGRESS_BAR = 1;
private final static int HIDE_PROGRESS_BAR = 0;
private BackgroundThread mBackgroundThread;
private TextView mText;
private Button mButton;
private ProgressBar mProgressBar;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_handler_example);
mBackgroundThread = new BackgroundThread();
mBackgroundThread.start();
mText = (TextView) findViewById(R.id.text);
mProgressBar = (ProgressBar) findViewById(R.id.progress);
mButton = (Button) findViewById(R.id.button);
mButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mBackgroundThread.doWork();
}
});
}
@Override
protected void onDestroy() {
super.onDestroy();
mBackgroundThread.exit();
}
private final Handler mUiHandler = new Handler() {
public void handleMessage(Message msg) {
switch(msg.what) {
case SHOW_PROGRESS_BAR:
mProgressBar.setVisibility(View.VISIBLE);
break;
case HIDE_PROGRESS_BAR:
mText.setText(String.valueOf(msg.arg1));
mProgressBar.setVisibility(View.INVISIBLE);
break;
}
}
};
private class BackgroundThread extends Thread {
private Handler mBackgroundHandler;
public void run() {
Looper.prepare();
mBackgroundHandler = new Handler();
Looper.loop();
}
public void doWork() {
mBackgroundHandler.post(new Runnable() {
@Override
public void run() {
Message uiMsg = mUiHandler.obtainMessage(SHOW_PROGRESS_BAR, 0,
0, null);
mUiHandler.sendMessage(uiMsg);
Random r = new Random();
int randomInt = r.nextInt(5000);
SystemClock.sleep(randomInt);
uiMsg = mUiHandler.obtainMessage(HIDE_PROGRESS_BAR, randomInt,
0, null);
mUiHandler.sendMessage(uiMsg);
}
});
}
public void exit() {
mBackgroundHandler.getLooper().quit();
}
}
}
救命 android執行緒間通訊 handler message之類的
執行緒間通訊（三種方式）：：
public class AnrActivity extends Activity implements OnClickListener {
TextView text;
Handler handler;
ProgressBar bar;
private class MyAsycnTask extends AsyncTask<URL, Integer, String>{
@Override
protected void onProgressUpdate(Integer... values) {
bar.setProgress(values[0]);
text.setText("進度："+values[0]+"%");
super.onProgressUpdate(values);
}
@Override
protected String doInBackground(URL... params) {
for (int i = 0; i <100; i++) {
try {
publishProgress(i+1);
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
return "success";
}
@Override
protected void onPostExecute(String result) {
text.setText(result);
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button down = (Button) this.findViewById(R.id.button1);
Button receiver = (Button) this.findViewById(R.id.button2);
Button update = (Button)this.findViewById(R.id.button3);
bar = (ProgressBar)this.findViewById(R.id.progressBar1);
text = (TextView)this.findViewById(R.id.text);
update.setOnClickListener(this);
down.setOnClickListener(this);
receiver.setOnClickListener(this);
}
@Override
public void onClick(final View v) {
switch (v.getId()) {
case R.id.button1:
//通過 Asycntask 進行通訊
MyAsycnTask myAsycnTask = new MyAsycnTask();
myAsycnT......餘下全文>>
面試被問到android中兩個子執行緒怎通訊，我懵了
構造HandlerThread類的物件mHandlerThread，這樣生成一個子執行緒可以呼叫new MyHandler(mHandlerThread.getLooper())來獲取子執行緒的handler，另一個子執行緒發訊息，收到訊息的就是子執行緒而不是主執行緒了。