前言
相信這樣一個問題,大傢都不會陌生,
“有什麼的方法可以使Android的程序APK不用安裝,而能夠直接啟動”。
發現最後的結局都是不能實現這個美好的願望,而騰訊Android手機遊戲平臺卻又能實現這個功能,下載的連連看,五子棋都沒有安裝過程,但是都能直接運行,這其中到底有什麼“玄機”呢,也有熱心童鞋問過我這個問題,本文就為大傢來揭開這個謎團。
實踐
我實現瞭一個小小的Demo,麻雀雖小五臟俱全,為瞭突出原理,我就盡量簡化瞭程序,通過這個實例來讓大傢明白後臺的工作原理。
下載demo的apk程序apks,其中包括瞭兩個apk,分別是A和B
這兩個APK可分別安裝和運行,A程序界面隻顯示一個Button,B程序界面會動態顯示當前的時間
下面的三幅圖片分別為直接啟動運行A程序(安裝TestA.apk),直接啟動運行B程序(安裝TestB.apk)和由A程序動態啟動B程序(安裝TestA.apk,TestB.apk不用安裝,而是放在/mnt/sdcard/目錄中,即SD卡上)的截圖,細心的同學可以停下來觀察一下他們之間的不同
後兩幅圖片的不同,也即Title的不同,則解釋出瞭我們將要分析的後臺實現原理的機制
實現原理
最能講明白道理的莫過於源碼瞭,下面我們就來分析一下A和B的實現機制,首先來分析TestA.apk的主要代碼實現:
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button btn = (Button) findViewById(R.id.btn);
btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Bundle paramBundle = new Bundle();
paramBundle.putBoolean("KEY_START_FROM_OTHER_ACTIVITY", true);
String dexpath = "/mnt/sdcard/TestB.apk";
String dexoutputpath = "/mnt/sdcard/";
LoadAPK(paramBundle, dexpath, dexoutputpath);
}
});
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button btn = (Button) findViewById(R.id.btn);
btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Bundle paramBundle = new Bundle();
paramBundle.putBoolean("KEY_START_FROM_OTHER_ACTIVITY", true);
String dexpath = "/mnt/sdcard/TestB.apk";
String dexoutputpath = "/mnt/sdcard/";
LoadAPK(paramBundle, dexpath, dexoutputpath);
}
});
}
代碼解析:這就是OnCreate函數要做的事情,裝載view界面,綁定button事件,大傢都熟悉瞭,還有就是設置程序B的放置路徑,因為我程序中代碼是從/mnt/sdcard/TestB.apk中動態加載,這也就是為什麼要讓大傢把TestB.apk放在SD卡上面的原因瞭。關鍵的函數就是最後一個瞭LoadAPK,它來實現動態加載B程序。
public void LoadAPK(Bundle paramBundle, String dexpath, String dexoutputpath) {
ClassLoader localClassLoader = ClassLoader.getSystemClassLoader();
DexClassLoader localDexClassLoader = new DexClassLoader(dexpath,
dexoutputpath, null, localClassLoader);
try {
PackageInfo plocalObject = getPackageManager()
.getPackageArchiveInfo(dexpath, 1);
if ((plocalObject.activities != null)
&& (plocalObject.activities.length > 0)) {
String activityname = plocalObject.activities[0].name;
Log.d(TAG, "activityname = " + activityname);
Class localClass = localDexClassLoader.loadClass(activityname);
Constructor localConstructor = localClass
.getConstructor(new Class[] {});
Object instance = localConstructor.newInstance(new Object[] {});
Log.d(TAG, "instance = " + instance);
Method localMethodSetActivity = localClass.getDeclaredMethod(
"setActivity", new Class[] { Activity.class });
localMethodSetActivity.setAccessible(true);
localMethodSetActivity.invoke(instance, new Object[] { this });
Method methodonCreate = localClass.getDeclaredMethod(
"onCreate", new Class[] { Bundle.class });
methodonCreate.setAccessible(true);
methodonCreate.invoke(instance, new Object[] { paramBundle });
}
return;
} catch (Exception ex) {
ex.printStackTrace();
}
}
public void LoadAPK(Bundle paramBundle, String dexpath, String dexoutputpath) {
ClassLoader localClassLoader = ClassLoader.getSystemClassLoader();
DexClassLoader localDexClassLoader = new DexClassLoader(dexpath,
dexoutputpath, null, localClassLoader);
try {
PackageInfo plocalObject = getPackageManager()
.getPackageArchiveInfo(dexpath, 1);
if ((plocalObject.activities != null)
&& (plocalObject.activities.length > 0)) {
String activityname = plocalObject.activities[0].name;
Log.d(TAG, "activityname = " + activityname);
Class localClass = localDexClassLoader.loadClass(activityname);
Constructor localConstructor = localClass
.getConstructor(new Class[] {});
Object instance = localConstructor.newInstance(new Object[] {});
Log.d(TAG, "instance = " + instance);
Method localMethodSetActivity = localClass.getDeclaredMethod(
"setActivity", new Class[] { Activity.class });
localMethodSetActivity.setAccessible(true);
localMethodSetActivity.invoke(instance, new Object[] { this });
Method methodonCreate = localClass.getDeclaredMethod(
"onCreate", new Class[] { Bundle.class });
methodonCreate.setAccessible(true);
methodonCreate.invoke(instance, new Object[] { paramBundle });
}
return;
} catch (Exception ex) {
ex.printStackTrace();
}
}
代碼解析:這個函數要做的工作如下:加載B程序的APK文件,通過類加載器DexClassLoader來解析APK文件,這樣會在SD卡上面生成一個同名的後綴為dex的文件,例如/mnt/sdcard/TestB.apk==>/mnt/sdcard/TestB.dex,接下來就是通過java反射機制,動態實例化B中的Activity對象,並依次調用瞭其中的兩個函數,分別為setActivity和onCreate.看到這裡,大傢是不是覺得有點奇怪,Activity的啟動函數是onCreate,為什麼要先調用setActivity,而更奇怪的是setActivity並不是系統的函數,確實,那是我們自定義的,這也就是核心的地方。
好瞭帶著這些疑問,我們再來分析B程序的主代碼:
public class TestBActivity extends Activity {
private static final String TAG = "TestBActivity";
private Activity otherActivity;
@Override
public void onCreate(Bundle savedInstanceState) {
boolean b = false;
if (savedInstanceState != null) {
b = savedInstanceState.getBoolean("KEY_START_FROM_OTHER_ACTIVITY", false);
if (b) {
this.otherActivity.setContentView(new TBSurfaceView(
this.otherActivity));
}
}
if (!b) {
super.onCreate(savedInstanceState);
// setContentView(R.layout.main);
setContentView(new TBSurfaceView(this));
}
}
public void setActivity(Activity paramActivity) {
Log.d(TAG, "setActivity…" + paramActivity);
this.otherActivity = paramActivity;
}
}
public class TestBActivity extends Activity {
private static final String TAG = "TestBActivity";
private Activity otherActivity;
@Override
public void onCreate(Bundle savedInstanceState) {
boolean b = false;
if (savedInstanceState != null) {
b = savedInstanceState.getBoolean("KEY_START_FROM_OTHER_ACTIVITY", false);
if (b) {
this.otherActivity.setContentView(new TBSurfaceView(
this.otherActivity));
}
}
if (!b) {
super.onCreate(savedInstanceState);
// setContentView(R.layout.main);
setContentView(new TBSurfaceView(this));
}
}
public void setActivity(Activity paramActivity) {
Log.d(TAG, "setActivity…" + paramActivity);
this.otherActivity = paramActivity;
}
}
代碼解析:看完程序B的實現機制,大傢是不是有種恍然大悟的感覺,這根本就是“偷梁換柱”嘛,是滴,程序B動態借用瞭程序A的上下文執行環境,這也就是上面後兩幅圖的差異,最後一幅圖運行的是B的程序,但是title表示的卻是A的信息,而沒有重新初始化自己的,實際上這也是不可能的,所以有些童鞋雖然通過java的反射機制,正確呼叫瞭被調程序的onCreate函數,但是期望的結果還是沒有出現,原因就是這個上下文環境沒有正確建立起來,但是若通過startActivity的方式來啟動APK的話,android系統會替你建立正確的執行時環境,所以就沒問題。至於那個TBSurfaceView,那就是自定義的一個view畫面,動態畫當前的時間
public class TBSurfaceView extends SurfaceView implements Callback, Runnable {
private SurfaceHolder sfh;
private Thread th;
private Canvas canvas;
private Paint paint;
public TBSurfaceView(Context context) {
super(context);
th = new Thread(this);
sfh = this.getHolder();
sfh.addCallback(this);
paint = new Paint();
paint.setAntiAlias(true);
paint.setColor(Color.RED);
this.setKeepScreenOn(true);
}
public void surfaceCreated(SurfaceHolder holder) {
th.start();
}
private void draw() {
try {
canvas = sfh.lockCanvas();
if (canvas != null) {
canvas.drawColor(Color.WHITE);
canvas.drawText("Time: " + System.currentTimeMillis(), 100,
100, paint);
}
} catch (Exception ex) {
ex.printStackTrace();
} finally {
if (canvas != null) {
sfh.unlockCanvasAndPost(canvas);
}
}
}
public void run() {
while (true) {
draw();
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
}
public void surfaceDestroyed(SurfaceHolder holder) {
}
}
public class TBSurfaceView extends SurfaceView implements Callback, Runnable {
private SurfaceHolder sfh;
private Thread th;
private Canvas canvas;
private Paint paint;
public TBSurfaceView(Context context) {
super(context);
th = new Thread(this);
sfh = this.getHolder();
sfh.addCallback(this);
paint = new Paint();
paint.setAntiAlias(true);
paint.setColor(Color.RED);
this.setKeepScreenOn(true);
}
public void surfaceCreated(SurfaceHolder holder) {
th.start();
}
private void draw() {
try {
canvas = sfh.lockCanvas();
if (canvas != null) {
canvas.drawColor(Color.WHITE);
canvas.drawText("Time: " + System.currentTimeMillis(), 100,
100, paint);
}
} catch (Exception ex) {
ex.printStackTrace();
} finally {
if (canvas != null) {
sfh.unlockCanvasAndPost(canvas);
}
}
}
public void run() {
while (true) {
draw();
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
}
public void surfaceDestroyed(SurfaceHolder holder) {
}
}
騰訊遊戲平臺解析
說瞭這麼多,都是背景,O(∩_∩)O哈哈~
其實騰訊遊戲平臺就是這麼個實現原理,我也是通過它才學習到這種方式的,還得好好感謝感謝呢。
騰訊Android遊戲平臺的遊戲分成兩類,第一類是騰訊自主研發的,像鬥地主,五子棋,連連看什麼的,所以實現機制就如上面的所示,A代表遊戲大廳,B代表鬥地主類的小遊戲。第二類是第三方軟件公司開發的,可就不能已這種方式來運作瞭,畢竟騰訊不能限制別人開發代碼的方式啊,所以騰訊就開放瞭一個sdk包出來,讓第三方應用可以和遊戲大廳相結合,具體可參見QQ遊戲中心開發者平臺,但這同時就損失瞭一個優點,那就是第三方開發的遊戲要通過安裝的方式才能運行。
結論
看到這裡,相信大傢都比較熟悉這個背後的原理瞭吧,也希望大傢能提供更好的反饋信息!
程序源碼下載source:http://up.aiwalls.com/2012/0429/20120429095938970.zip
摘自 潤物無聲