Android -- 经验分享

代码中安装apk判断某个apk是否已经安装取得屏幕大小获得 LayoutInflater 实例的三种方式ContentResolver.query()，以及 Activity.managedQuery异同解锁功能点亮屏幕activity全屏显示屏常亮代码SQL中 inner join、 left join 、right join、 outer join之间的区别包含button的item也能弹出菜单，回调click以及long click的监听器背光亮度   /sys/class/leds/lcd-backlight/brightness判断是否在锁屏界面的函数OnTouchListener实现双击事件回到待机界面定时器相关sd卡和sim卡状态判断开机启动，检查sim卡是否发生变更代码中安装apk                                                                             

Runtime.getRuntime().exec("pm install xxx.apk");

需要在manifest.xml文件中，加上INSTALL_PACKAGES的权限，可以用 Package install的receiver来处理安装成功后的操作或者:/*** 安装apk* @param url*/private void installApk(String saveFileName){File apkfile = new File(saveFileName);if (!apkfile.exists()) {return;}Intent i = new Intent(Intent.ACTION_VIEW);i.setDataAndType(Uri.parse("file://" + apkfile.toString()), "application/vnd.android.package-archive");mContext.startActivity(i);}

判断某个APK是否已经安装                                                            

<span style="font-size:18px;">private boolean isAppInstalled(String uri){PackageManager pm = getPackageManager();boolean installed =false;try{pm.getPackageInfo(uri,PackageManager.GET_ACTIVITIES);installed =true;}catch(PackageManager.NameNotFoundException e){installed =false;}return installed;}</span>

<span style="font-size:18px;">//Just call the method by passing the package name of the application you need to check.if(isAppInstalled("com.yourpackage.package")){//app installed}else{//app not installed}</span>

取得屏幕大小      1、在非activity类中

WindowManager windowManager = (WindowManager)(mContext.getSystemService(Context.WINDOW_SERVICE));int screenWidth = windowManager.getDefaultDisplay().getWidth();int screenHeight = windowManager.getDefaultDisplay().getHeight();

2、在activity类中

int screenWidth  = getWindowManager().getDefaultDisplay().getWidth();       // 屏幕宽（像素，如：480px）int screenHeight = getWindowManager().getDefaultDisplay().getHeight();      // 屏幕高（像素，如：800px）

获得 LayoutInflater 实例的三种方式                                             

LayoutInflater inflater = getLayoutInflater();  //调用Activity的getLayoutInflater()LayoutInflater localinflater =(LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);LayoutInflater inflater = LayoutInflater.from(context);

示意代码：

LayoutInflater inflater = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);View view = inflater.inflate(R.layout.custom, (ViewGroup)findViewById(R.id.test));

对于上面代码，指定了第二个参数 ViewGroup root，当然你也可以设置为 null 值。ContentResolver.query()，以及 Activity.managedQuery异同参数、返回值相同：都返回 Cursor 对象参数：

URI:  Content Provider 需要返回的资源索引Projection: 用于标识有哪些columns需要包含在返回数据中。Selection: 作为查询符合条件的过滤参数，类似于SQL语句中Where之后的条件判断。SelectionArgs: 同上。SortOrder: 用于对返回信息进行排序。

不同：mContext.getContentResolver().queryContentResolver.query()，以及 Activity.managedQuery()所以，我们看到一个是ContentResolver提供的查询方法，位于android.content.ContextWrapper.getContentResolver()，另一个则为Activity。  Activity.managedQuery()  方法导致活动管理 Cursor 的生命周期解锁功能                                                                                      

KeyguardManager keyguardManager = (KeyguardManager)getSystemService(KEYGUARD_SERVICE);KeyguardLock keyguardLock = keyguardManager.newKeyguardLock("");keyguardLock.disableKeyguard();PowerManager pm = (PowerManager)getSystemService(POWER_SERVICE);

点亮屏幕                                                                                      

PowerManager pm = (PowerManager)getSystemService(POWER_SERVICE);WakeLock mWakelock = pm.newWakeLock(PowerManager.ACQUIRE_CAUSES_WAKEUP|PowerManager.SCREEN_DIM_WAKE_LOCK,"SimpleTimer");mWakeLock.acquire();//点亮mWakeLock.release();//关闭

activity全屏显示                                                                          

getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);requestWindowFeature(Window.FEATURE_NO_TITLE);

注意；要在setContentView(R.layout.layout)语句之前调用才行。屏常亮代码                                                                                   

getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);//屏常亮

SQL中 inner join、 left join 、right join、 outer join之间的区别举例说明

A表(a1,b1,c1)      B表(a2,b2)a1   b1   c1        a2    b201   数学 95         01    张三02   语文 90         02    李四03   英语 80         04    王五

select A.*,B.* from A  inner join B on(A.a1=B.a2)

结果是：a1   b1   c1       a2    b201   数学 95       01    张三02   语文 90       02    李四

select A.*,B.* from A  left outer join B on(A.a1=B.a2)

结果是:a1   b1   c1       a2    b201   数学 95       01    张三02   语文 90       02    李四03   英语 80       NULL  NULL

select A.*,B.* from A  right outer join B on(A.a1=B.a2)

结果是:a1   b1   c1       a2    b201   数学 95       01    张三02   语文 90       02    李四NULL NULL NULL     04    王五

select A.*,B.* from A  full outer join B on(A.a1=B.a2)

结果是:a1   b1   c1       a2    b201   数学 95       01    张三02   语文 90       02    李四03   英语 80       NULL  NULLNULL NULL NULL     04    王五

听器  设置button属性：

android:focusable="false"

外还要设置 listview属性：

android:longClickable="true"

PS: 如果包含的Button是ImageButton，那么在xml中设置了android:focusable="false"属性在当前版本是无效的，必须在代码中，再次呼叫函数ImageButton.setFocusable（false）设置一次。 或者在父Item里面加上

android:descendantFocusability="blocksDescendants"

背光亮度例如

echo 255 > /sys/class/leds/lcd-backlight/brightness

代码修改亮度：

Settings.System.putInt(getContentResolver(), SCREEN_BRIGHTNESS, brightness);    //brightness 背光亮度 0~255Settings.System.putInt(getContentResolver(),SCREEN_OFF_TIMEOUT, timeoutValues);//timeoutValues 灭屏时间 ms

判断是否在锁屏界面的函数                                                              

KeyguardManager： inKeyguardRestrictedInputMode();

例：

KeyguardManager km = (KeyguardManager)getSystemService(Context.KEYGUARD_SERVICE);boolean keyguardexist = km.inKeyguardRestrictedInputMode();

OnTouchListener实现双击事件                                                    

class MyOnTouchListener implements View.OnTouchListener{private long mLastTime = 0;private long mCurTime = 0;@Overridepublic boolean onTouch(View v, MotionEvent event) {if(MotionEvent.ACTION_DOWN == event.getAction()){mLastTime = mCurTime;mCurTime = System.currentTimeMillis();if (mCurTime - mLastTime < 1000) {// 双击事件  关闭activityFullBlackActivity.this.finish();return true;}}return false;}}

回到待机界面                                                                                

Intent home = new Intent(Intent.ACTION_MAIN);home.addCategory(Intent.CATEGORY_HOME);this.startActivity(home);

定时器相关                                                                                   采用Handler与线程的sleep(long)方法Handler主要用来处理接受到的消息。1. 定义一个Handler类，用于处理接受到的Message。

Handler handler = new Handler() {public void handleMessage(Message msg) {// 要做的事情super.handleMessage(msg);}};

新建一个实现Runnable接口的线程类，如下：

public class MyThread implements Runnable {@Overridepublic void run() {// TODO Auto-generated method stubwhile (true) {try {Thread.sleep(10000);// 线程暂停10秒，单位毫秒Message message = new Message();message.what = 1;handler.sendMessage(message);// 发送消息} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}}

3. 在需要启动线程的地方加入下面语句：

new Thread(new MyThread()).start();

4. 启动线程后，线程每10s发送一次消息。采用Handler的postDelayed(Runnable, long)方法1. 定义一个Handler类

Handler handler=new Handler();Runnable runnable=new Runnable() {@Overridepublic void run() {// TODO Auto-generated method stub//要做的事情handler.postDelayed(this, 2000);}};

2. 启动计时器

handler.postDelayed(runnable, 2000);//每两秒执行一次runnable.

3. 停止计时器

handler.removeCallbacks(runnable);

采用Handler与timer及TimerTask结合的方法1. 定义定时器、定时器任务及Handler句柄

private final Timer timer = new Timer();private TimerTask task;Handler handler = new Handler() {@Overridepublic void handleMessage(Message msg) {// TODO Auto-generated method stub// 要做的事情super.handleMessage(msg);}};

2. 初始化计时器任务

task = new TimerTask() {@Overridepublic void run() {// TODO Auto-generated method stubMessage message = new Message();message.what = 1;handler.sendMessage(message);}};

3. 启动定时器

timer.schedule(task, 2000, 2000);

简要说一下上面三步提到的一些内容：1. 定时器任务（TimerTask）顾名思义，就是说当定时器到达指定的时间时要做的工作，这里是想Handler发送一个消息，由Handler类进行处理。2. java.util.Timer.schedule(TimerTask task, long delay, long period)：这个方法是说，delay/1000秒后执行task,然后进过period/1000秒再次执行task，这个用于循环任务，执行无数次，当然，你可以用timer.cancel();取消计时器的执行。闹钟定时

AlarmManager am = (AlarmManager) mContext.getSystemService(Context.ALARM_SERVICE);PendingIntent pendingIntent = PendingIntent.getBroadcast(mContext, 0, new Intent(SEND_SMS_BEGIN), 0);am.set(AlarmManager.RTC_WAKEUP, 60*1000, pendingIntent);

耳机状态                                                                                      

private static final String HEADSET_STATE_PATH = "/sys/class/switch/h2w/state";    //保存状态文件位置private boolean isHeadsetExists(){       //判断耳机是否插入的函数    FM源码 FMplayService.javachar[] buffer = new char[1024];int newState = 0;try {FileReader file = new FileReader(HEADSET_STATE_PATH);int len = file.read(buffer, 0, 1024);newState = Integer.valueOf((new String(buffer, 0, len)).trim());} catch (FileNotFoundException e) {Log.e(LOGTAG, "This kernel does not have wired headset support");} catch (Exception e) {Log.e(LOGTAG, "" , e);}return newState != 0;}

未插入耳机：# cat /sys/class/switch/h2w/statecat /sys/class/switch/h2w/state0插入耳机：# cat /sys/class/switch/h2w/statecat /sys/class/switch/h2w/state1

sd卡和sim卡状态判断                                                                   

//sdcard是否可读写public boolean IsCanUseSdCard() {try {return Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED);} catch (Exception e) {e.printStackTrace();}return false;}//sim卡是否可读public boolean isCanUseSim() {try {TelephonyManager mgr = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);return TelephonyManager.SIM_STATE_READY == mgr.getSimState();} catch (Exception e) {e.printStackTrace();}return false;}

开机启动，检查sim卡是否发生变更                                                  （1）注册receiver，设置意图过滤器

<receiver android:name=".receiver.BootCompleteReceiver" ><intent-filter android:priority="1000" ><action android:name="android.intent.action.BOOT_COMPLETED" /></intent-filter></receiver>

（2）接受开机广播，并判断sim卡时候发生更改

public class BootCompleteReceiver extends BroadcastReceiver {private static final String TAG = "BootCompleteReceiver";private SharedPreferences sp;private TelephonyManager tm;@Overridepublic void onReceive(Context context, Intent intent) {Log.i(TAG,"手机重启了");sp = context.getSharedPreferences("config", Context.MODE_PRIVATE);boolean protecting = sp.getBoolean("protecting", false);//如果防盗保护开启if(protecting){//判断sim卡是否发生了变化tm = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);String currentSim = tm.getSimSerialNumber();String savedSim= sp.getString("sim", "");if(savedSim.equals(currentSim)){// sim卡为发生变化， do nothint}else{//sim卡发生了变化//发送报警短信 给安全号码SmsManager smsManager = SmsManager.getDefault();String destinationAddretss = sp.getString("safenumber", "");smsManager.sendTextMessage(destinationAddretss, null, "sim change !!!", null, null);}}}}

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