[英]Android Application - Resume Thread
我有一个运行有线程的类的Android应用程序。 基本上和这里一样 。
目前该线程每500毫秒更新一次具有计算值的文本视图,并另外记录该值,因此我可以在adb-logcat中看到它。
当我使用设备的后退按钮退出应用程序时,线程仍在后台运行。 (这就是我想要的)。 adb-logcat仍然提供线程正在计算的值。
但是当我重新打开应用程序时,textview不再更新!
我该怎么做,当我再次打开应用程序时,它可以恢复更新textview?
这是我的简化代码:
SensorProcessor.java
public class SensorProcessor implements Runnable {
protected Context mContext;
protected Activity mActivity;
private volatile boolean running = true;
//Tag for Logging
private final String LOG_TAG = SensorProcessor.class.getSimpleName();
public SensorProcessor(Context mContext, Activity mActivity){
this.mContext = mContext;
this.mActivity = mActivity;
}
public void run() {
while (running){
try {
final String raw = getSensorValue();
mActivity.runOnUiThread(new Runnable() {
public void run() {
final TextView textfield_sensor_value;
textfield_sensor_value = (TextView) mActivity.findViewById(R.id.text_sensor);
textfield_sensor_value.setText("Sensor Value: " + raw); // <-------- Does not update the field, when app resumes
Log.v(LOG_TAG, raw); // <-------- Still working after the app resumes
}
});
Thread.sleep(100);
} catch (InterruptedException e) {
//When an interrupt is called, we set running to false, so the thread can exit nicely
running = false;
}
}
Log.v(LOG_TAG, "Sensor Thread finished");
}
}
MainActivity.java
public class MainActivity extends Activity implements OnClickListener, OnInitListener {
//Start the Thread, when the button is clicked
public void onClick(View v) {
if (v.getId() == R.id.button_start) {
runnable = new SensorProcessor(this.getApplicationContext(),this);
thread = new Thread(runnable);
thread.start();
}
}
您可以扩展Application类,并在其中将getter和setter方法插入Runnable。 这是manifest.xml中MyApplication的示例(不要忘记添加清单连接!):
<application
android:name=".MyApplication"
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppBaseTheme" >
然后是MyApplication:
public class MyApplication extends Application {
private SensorProcessor mSensorProcessor = null;
public SensorProcessor getCurrentSensorProcessor(){
return mSensorProcessor;
}
public void setSensorProcessor(SensorProcessor mSensorProcessor){
this.mSensorProcessor = mSensorProcessor;
}
}
通过调用在您的活动的onCreate()中:
((MyApplication)getApplication()).getCurrentSensorProcessor().mActivity = this;
您还需要修改Runnable构造函数:
public SensorProcessor(Context mContext, Activity mActivity){
this.mContext = mContext;
this.mActivity = mActivity;
((MyApplication)mActivity.getApplication()).setSensorProcessor(this);
}
并且不要忘记在完成时通过在Runnable内部调用mSensorProcessor实例来清空它:
((MyApplication)mActivity.getApplication()).setSensorProcessor(null);
最后,您需要在“活动”中修改onClick:
if (v.getId() == R.id.button_start) {
SensorProcessor mSensorProcessor = ((MyApplication)getApplication()).getCurrentSensorProcessor();
if (mSensorProcessor != null)
mSensorProcessor.mActivity = this;
else {
runnable = new SensorProcessor(this.getApplicationContext(), this);
thread = new Thread(runnable);
thread.start();
}
}
它应该可以工作,也许需要进行一些小的更改。
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