android的電量一直是所有人關注的問題，

電池越來越大，使用起來沒有任何改善，有人覺得是螢幕越來越大導致的，但是實際上更多的是app的不注意，導致的浪費了很多電量。

從本章開始，我們將從開發的角度來告訴大家，如何使我們的應用更加省電的一些技巧。

JobSchedule

這個是Android 5.0之後，考慮到截止我寫這篇文章的時候，Android 5.0以上的使用者已經增加到25.1%，我覺的在開發中，建議使用JobSchedule來規範我們的開發。

功能：JobSchedule的作用就是將我們需要定時或者特定條件的事件交給系統，當系統滿足條件的時候，就會回撥我們的元件，執行我們的程式碼，並且在執行的過程中會回撥我們的方法，

條件：在剛剛我說了在特定條件，這個當然不是隨便的條件，而是規定好的，（我總結了4+1種條件）

條件1：網路可用

條件2：定時

條件3：手機處於空閒狀態

條件4：手機是否處於供電穩定狀態（充電）

這個也並非只是插入充電器，而且還要在電池處於健康狀態的情況下才會觸發，一般來說是手機電量

條件+1：迴圈執行（被列入+1是因為這個需要前四個觸發之後才有用處，當然你也可以把它歸為定時）

使用方法：

        ComponentName mServiceComponent = new ComponentName(this, TestJobService.class);           //當事件滿足的時候，呼叫的元件
        JobInfo.Builder builder = new JobInfo.Builder(i, mServiceComponent);                       //i為int值，當前事件的
        JobScheduler tm =(JobScheduler) getSystemService(Context.JOB_SCHEDULER_SERVICE);
        tm.schedule(builder);
 

下面依次對每一種觸發進行設定：

網路觸發：

builder.setRequiredNetworkType(JobInfo.NETWORK_TYPE_UNMETERED);                //設定為不限制流量的條件觸發，可以認為是wifi條件下觸發
builder.setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY);                                 //有網路連線的時候觸發

定時：

builder.setOverrideDeadline(time); //其實這裡與我們所想的用法又有所區別，他並沒有單獨提供介面，而是複用，這個方法在後面有另一種用法的介紹。

手機處於空閒狀態：

builder.setRequiresDeviceIdle(true/*false*/);                                                                          //設定為空閒狀態觸發

手機是否處於供電穩定狀態

builder.setRequiresCharging(true/*false*/);                                                                           //手機是否處於充電狀態

除了這些條件之外還可以進行一些其他的設定來控制觸發狀態

builder.setMinimumLatency(time);                                                                                          //time的單位是s，作用是滿足觸發條件也要延時time 豪秒之後再觸發

builder.setOverrideDeadline(time);                                                                                        //time的單位是s，作用是設定time豪秒之後，如果沒有任何觸發也執行

builder.setPeriodic(time);                                                                                                         //設定迴圈觸發，否則觸發一次就結束了，這樣可以間隔time豪秒之後，還是可以觸發

builder.setPersisted(true/*false*/);                               //設定觸發條件是否重啟手機後仍有效。         /這個它是通過將presist的資訊，寫到了/data/system/job/jobs.xml檔案中了

builder.setExtras(PersistableBundle extra);                     //設定startJob時，帶有Bundle

builder.setBackoffCriteria(Long.valueOf(backoffTime) * 1000, backoffPolicy);           //這個是比較特殊的，這個是當意外發生的時候，多久之後，重新執行，分為線性計算和指數計算，

綜上就是JobSchedule的基本使用方法，

/*
 * Copyright 2014 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.jobscheduler.service;

import android.app.job.JobInfo;
import android.app.job.JobScheduler;
import android.app.job.JobParameters;
import android.app.job.JobService;
import android.content.Context;
import android.content.Intent;
import android.os.Message;
import android.os.Messenger;
import android.os.RemoteException;
import android.util.Log;

import com.example.android.jobscheduler.MainActivity;

import java.util.LinkedList;


/**
 * Service to handle callbacks from the JobScheduler. Requests scheduled with the JobScheduler
 * ultimately land on this service's "onStartJob" method. Currently all this does is post a message
 * to the app's main activity to change the state of the UI.
 */
public class TestJobService extends JobService {
    private static final String TAG = "SyncService";

    @Override
    public void onCreate() {
        super.onCreate();
        Log.i(TAG, "Service created");
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.i(TAG, "Service destroyed");
    }

    /**
     * When the app's MainActivity is created, it starts this service. This is so that the
     * activity and this service can communicate back and forth. See "setUiCalback()"
     */
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Messenger callback = intent.getParcelableExtra("messenger");
        Message m = Message.obtain();
        m.what = MainActivity.MSG_SERVICE_OBJ;
        m.obj = this;
        try {
            callback.send(m);
        } catch (RemoteException e) {
            Log.e(TAG, "Error passing service object back to activity.");
        }
        return START_NOT_STICKY;
    }

    @Override
    public boolean onStartJob(JobParameters params) {
        // We don't do any real 'work' in this sample app. All we'll
        // do is track which jobs have landed on our service, and
        // update the UI accordingly.
        jobParamsMap.add(params);
        if (mActivity != null) {
            mActivity.onReceivedStartJob(params);
        }
        Log.i(TAG, "on start job: " + params.getJobId());
        return true;
    }

    @Override
    public boolean onStopJob(JobParameters params) {
        // Stop tracking these job parameters, as we've 'finished' executing.
        jobParamsMap.remove(params);
        if (mActivity != null) {
            mActivity.onReceivedStopJob();
        }
        Log.i(TAG, "on stop job: " + params.getJobId());
        return true;
    }

    MainActivity mActivity;
    private final LinkedList<JobParameters> jobParamsMap = new LinkedList<JobParameters>();

    public void setUiCallback(MainActivity activity) {
        mActivity = activity;
    }

    /** Send job to the JobScheduler. */
    public void scheduleJob(JobInfo t) {
        Log.d(TAG, "Scheduling job");
        JobScheduler tm =
                (JobScheduler) getSystemService(Context.JOB_SCHEDULER_SERVICE);
        tm.schedule(t);
    }

    /**
     * Not currently used, but as an exercise you can hook this
     * up to a button in the UI to finish a job that has landed
     * in onStartJob().
     */
    public boolean callJobFinished() {
        JobParameters params = jobParamsMap.poll();
        if (params == null) {
            return false;
        } else {
            jobFinished(params, false);
            return true;
        }
    }

}

/*
 * Copyright 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.jobscheduler;

import android.app.Activity;
import android.app.job.JobInfo;
import android.app.job.JobParameters;
import android.app.job.JobScheduler;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.res.Resources;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.os.Messenger;
import android.text.TextUtils;
import android.view.View;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.TextView;
import android.widget.Toast;

import com.example.android.jobscheduler.service.TestJobService;

public class MainActivity extends Activity {

    private static final String TAG = "MainActivity";

    public static final int MSG_UNCOLOUR_START = 0;
    public static final int MSG_UNCOLOUR_STOP = 1;
    public static final int MSG_SERVICE_OBJ = 2;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.sample_main);
        Resources res = getResources();
        defaultColor = res.getColor(R.color.none_received);
        startJobColor = res.getColor(R.color.start_received);
        stopJobColor = res.getColor(R.color.stop_received);

        // Set up UI.
        mShowStartView = (TextView) findViewById(R.id.onstart_textview);
        mShowStopView = (TextView) findViewById(R.id.onstop_textview);
        mParamsTextView = (TextView) findViewById(R.id.task_params);
        mDelayEditText = (EditText) findViewById(R.id.delay_time);
        mDeadlineEditText = (EditText) findViewById(R.id.deadline_time);
        mWiFiConnectivityRadioButton = (RadioButton) findViewById(R.id.checkbox_unmetered);
        mAnyConnectivityRadioButton = (RadioButton) findViewById(R.id.checkbox_any);
        mRequiresChargingCheckBox = (CheckBox) findViewById(R.id.checkbox_charging);
        mRequiresIdleCheckbox = (CheckBox) findViewById(R.id.checkbox_idle);
        mServiceComponent = new ComponentName(this, TestJobService.class);
        // Start service and provide it a way to communicate with us.
        Intent startServiceIntent = new Intent(this, TestJobService.class);
        startServiceIntent.putExtra("messenger", new Messenger(mHandler));
        startService(startServiceIntent);
    }
    // UI fields.
    int defaultColor;
    int startJobColor;
    int stopJobColor;

    private TextView mShowStartView;
    private TextView mShowStopView;
    private TextView mParamsTextView;
    private EditText mDelayEditText;
    private EditText mDeadlineEditText;
    private RadioButton mWiFiConnectivityRadioButton;
    private RadioButton mAnyConnectivityRadioButton;
    private CheckBox mRequiresChargingCheckBox;
    private CheckBox mRequiresIdleCheckbox;

    ComponentName mServiceComponent;
    /** Service object to interact scheduled jobs. */
    TestJobService mTestService;

    private static int kJobId = 0;

    Handler mHandler = new Handler(/* default looper */) {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case MSG_UNCOLOUR_START:
                    mShowStartView.setBackgroundColor(defaultColor);
                    break;
                case MSG_UNCOLOUR_STOP:
                    mShowStopView.setBackgroundColor(defaultColor);
                    break;
                case MSG_SERVICE_OBJ:
                    mTestService = (TestJobService) msg.obj;
                    mTestService.setUiCallback(MainActivity.this);
            }
        }
    };

    private boolean ensureTestService() {
        if (mTestService == null) {
            Toast.makeText(MainActivity.this, "Service null, never got callback?",
                    Toast.LENGTH_SHORT).show();
            return false;
        }
        return true;
    }

    /**
     * UI onclick listener to schedule a job. What this job is is defined in
     * TestJobService#scheduleJob().
     */
    public void scheduleJob(View v) {
        if (!ensureTestService()) {
            return;
        }

        JobInfo.Builder builder = new JobInfo.Builder(kJobId++, mServiceComponent);

        String delay = mDelayEditText.getText().toString();
        if (delay != null && !TextUtils.isEmpty(delay)) {
            builder.setMinimumLatency(Long.valueOf(delay) * 1000);
        }
        String deadline = mDeadlineEditText.getText().toString();
        if (deadline != null && !TextUtils.isEmpty(deadline)) {
            builder.setOverrideDeadline(Long.valueOf(deadline) * 1000);
        }
        boolean requiresUnmetered = mWiFiConnectivityRadioButton.isChecked();
        boolean requiresAnyConnectivity = mAnyConnectivityRadioButton.isChecked();
        if (requiresUnmetered) {
            builder.setRequiredNetworkType(JobInfo.NETWORK_TYPE_UNMETERED);
        } else if (requiresAnyConnectivity) {
            builder.setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY);
        }
        builder.setRequiresDeviceIdle(mRequiresIdleCheckbox.isChecked());
        builder.setRequiresCharging(mRequiresChargingCheckBox.isChecked());

        mTestService.scheduleJob(builder.build());

    }

    public void cancelAllJobs(View v) {
        JobScheduler tm =
                (JobScheduler) getSystemService(Context.JOB_SCHEDULER_SERVICE);
        tm.cancelAll();
    }

    /**
     * UI onclick listener to call jobFinished() in our service.
     */
    public void finishJob(View v) {
        if (!ensureTestService()) {
            return;
        }
        mTestService.callJobFinished();
        mParamsTextView.setText("");
    }

    /**
     * Receives callback from the service when a job has landed
     * on the app. Colours the UI and post a message to
     * uncolour it after a second.
     */
    public void onReceivedStartJob(JobParameters params) {
        mShowStartView.setBackgroundColor(startJobColor);
        Message m = Message.obtain(mHandler, MSG_UNCOLOUR_START);
        mHandler.sendMessageDelayed(m, 1000L); // uncolour in 1 second.
        mParamsTextView.setText("Executing: " + params.getJobId() + " " + params.getExtras());
    }

    /**
     * Receives callback from the service when a job that
     * previously landed on the app must stop executing.
     * Colours the UI and post a message to uncolour it after a
     * second.
     */
    public void onReceivedStopJob() {
        mShowStopView.setBackgroundColor(stopJobColor);
        Message m = Message.obtain(mHandler, MSG_UNCOLOUR_STOP);
        mHandler.sendMessageDelayed(m, 2000L); // uncolour in 1 second.
        mParamsTextView.setText("");
    }
}