WorkManager是Android自最新的支持包androidx引入的后台任务框架。和JobSchedule 相似,是JobSchedule 的改进。
WorkManager可实现:
一次性执行任务,链式执行任务,周期性执行任务,一定条件下(网络,电量)执行任务,设备重启后执行上次未完成任务等。
在Android studio中build.gradle引入WorkManager:
implementation "androidx.work:work-runtime:2.0.1"
因为Androidx和过去android的支持包不兼容,需要配置:
android.useAndroidX=true
android.enableJetifier=true
package zhangphil.app;
import android.content.Context;
import android.os.SystemClock;
import androidx.annotation.NonNull;
import androidx.work.Data;
import androidx.work.Worker;
import androidx.work.WorkerParameters;
import java.text.SimpleDateFormat;
import java.util.Date;
public class MyWorker extends Worker {
private SimpleDateFormat mSimpleDateFormat = new SimpleDateFormat("HH:mm:ss:SSS");
private Date mDate = new Date();
public MyWorker(@NonNull Context context, @NonNull WorkerParameters workerParams) {
super(context, workerParams);
}
@NonNull
@Override
public Result doWork() {
int n = getInputData().getInt(MainActivity.KEY, 1);
System.out.println(n + "," + getId() + "开始任务doWork()");
SystemClock.sleep(3000);
mDate.setTime(System.currentTimeMillis());
Data outputData = new Data.Builder()
.putString(MainActivity.KEY, n + "@" + mSimpleDateFormat.format(mDate) + "#" + getId())
.build();
return Result.success(outputData);
}
@Override
public void onStopped() {
super.onStopped();
System.out.println("任务onStop()");
}
}
package zhangphil.app;
import android.os.Bundle;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
import androidx.lifecycle.LiveData;
import androidx.lifecycle.Observer;
import androidx.work.Constraints;
import androidx.work.Data;
import androidx.work.NetworkType;
import androidx.work.OneTimeWorkRequest;
import androidx.work.Operation;
import androidx.work.WorkInfo;
import androidx.work.WorkManager;
import java.util.List;
import java.util.concurrent.TimeUnit;
public class MainActivity extends AppCompatActivity {
public static String KEY = "KEY";
private String TAG = "tag";
private TextView text;
private String string = "";
private static int VALUE = 1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
text = findViewById(R.id.text);
Data myData = new Data.Builder()
.putInt(KEY, VALUE++)
.build();
//约束条件。
Constraints constraints = new Constraints.Builder()
.setRequiresBatteryNotLow(true)
.setRequiredNetworkType(NetworkType.NOT_REQUIRED)
.build();
OneTimeWorkRequest.Builder argsWorkBuilder = new OneTimeWorkRequest.Builder(MyWorker.class)
.setConstraints(constraints)
.setInitialDelay(1, TimeUnit.SECONDS)
.setInputData(myData);
OneTimeWorkRequest request = argsWorkBuilder
.addTag(TAG)
.build();
System.out.println(request.getId() + "进入onCreate()");
LiveData<List<WorkInfo>> liveData = WorkManager.getInstance().getWorkInfosByTagLiveData(TAG);
liveData.observe(this, new Observer<List<WorkInfo>>() {
@Override
public void onChanged(List<WorkInfo> workInfos) {
for (WorkInfo workInfo : workInfos) {
if (workInfo != null && workInfo.getState() == WorkInfo.State.SUCCEEDED) {
display(workInfo.getOutputData().getString(KEY));
}
}
}
});
Operation operation = WorkManager.getInstance()
.enqueue(request);
//取消任务。
//WorkManager.getInstance().cancelWorkById(request.getId());
}
private void display(String s) {
string = string + s + "\n";
text.setText(string);
}
}
WorkManager可以执行链式任务,假设有下面的任务链:
那么可以这么写链式任务:
WorkContinuation chain1 = WorkManager.getInstance()
.beginWith(workA)
.then(workB);
WorkContinuation chain2 = WorkManager.getInstance()
.beginWith(workC)
.then(workD);
WorkContinuation chain3 = WorkContinuation
.combine(chain1, chain2)
.then(workE);
chain3.enqueue();