StartActivity的内部代码实现原理
2012-07-11 00:00
197 查看
1. 首先调用Activity的startActivity，-1表示 target Activity finish的时候不通知original Activity
public void startActivity(Intent intent) {
startActivityForResult(intent, -1);
}
2 . 调用Activityd的startActivityForResult方法,Instrumentation class 里面有一个ActivityMonitor 的内部类，用来监控view和system的交互
public void startActivityForResult(Intent intent, int requestCode) {
if (mParent == null) {
Instrumentation.ActivityResult ar =
mInstrumentation.execStartActivity(
this, mMainThread.getApplicationThread(), mToken, this,
intent, requestCode);
if (ar != null) {
mMainThread.sendActivityResult(
mToken, mEmbeddedID, requestCode, ar.getResultCode(),
ar.getResultData());
}
if (requestCode >= 0) {
// If this start is requesting a result, we can avoid making
// the activity visible until the result is received. Setting
// this code during onCreate(Bundle savedInstanceState) or onResume() will keep the
// activity hidden during this time, to avoid flickering.
// This can only be done when a result is requested because
// that guarantees we will get information back when the
// activity is finished, no matter what happens to it.
mStartedActivity = true;
}
} else {
mParent.startActivityFromChild(this, intent, requestCode);
}
}
3. 调用Instrumentation class的 ExecStartActivity：
public ActivityResult execStartActivity(
Context who, IBinder contextThread, IBinder token, Activity target,
Intent intent, int requestCode) {
IApplicationThread whoThread = (IApplicationThread) contextThread;
// 如果找到匹配的Activity，am.mHits++
if (mActivityMonitors != null) {
synchronized (mSync) {
final int N = mActivityMonitors.size();
for (int i=0; i<N; i++) {
final ActivityMonitor am = mActivityMonitors.get(i);
if (am.match(who, null, intent)) {
am.mHits++;
if (am.isBlocking()) {
return requestCode >= 0 ? am.getResult() : null;
}
break;
}
}
}
}
try {
//调用ActivityManagerProxy的startActivity方法
int result = ActivityManagerNative.getDefault()
.startActivity(whoThread, intent,
intent.resolveTypeIfNeeded(who.getContentResolver()),
null, 0, token, target != null ? target.mEmbeddedID : null,
requestCode, false, false);
checkStartActivityResult(result, intent);
} catch (RemoteException e) {
}
return null;
}
4. ActivityManagerProxy 的startActivity的具体实现：
public int startActivity(IApplicationThread caller, Intent intent, String resolvedType, Uri[] grantedUriPermissions, int grantedMode, IBinder resultTo, String resultWho, int requestCode, boolean onlyIfNeeded, boolean debug) throws RemoteException {
// Parcel 本质上把它当成一个Serialize就可以了，只是它是在内存中完成的序列化和反序列化，利用的是连续的内存空间(这里不要作为重点) Parcel data = Parcel.obtain(); Parcel reply = Parcel.obtain(); data.writeInterfaceToken(IActivityManager.descriptor); data.writeStrongBinder(caller != null ? caller.asBinder() : null); intent.writeToParcel(data, 0); data.writeString(resolvedType); data.writeTypedArray(grantedUriPermissions, 0); data.writeInt(grantedMode); data.writeStrongBinder(resultTo); data.writeString(resultWho); data.writeInt(requestCode); data.writeInt(onlyIfNeeded ? 1 : 0); data.writeInt(debug ? 1 : 0);
//具体请参照后面的代码 （这个函数只看到这里就好了！！！） mRemote.transact(START_ACTIVITY_TRANSACTION, data, reply, 0); reply.readException(); int result = reply.readInt(); reply.recycle(); data.recycle(); return result; }
//清除sOwnedPool中parcel对象，返回一个新的parcel
public static Parcel obtain() {
final Parcel[] pool = sOwnedPool;
synchronized (pool) {
Parcel p;
for (int i=0; i<POOL_SIZE; i++) {
p = pool[i];
if (p != null) {
pool[i] = null;
if (DEBUG_RECYCLE) {
p.mStack = new RuntimeException();
}
return p;
}
}
}
return new Parcel(0);
}
// 清除pool中存储parcel,通过jni free刚才分配的内存
public final void recycle() {
if (DEBUG_RECYCLE) mStack = null;
freeBuffer();
final Parcel[] pool = mOwnObject != 0 ? sOwnedPool : sHolderPool;
synchronized (pool) {
for (int i=0; i<POOL_SIZE; i++) {
if (pool[i] == null) {
pool[i] = this;
return;
}
}
}
}
//
private native void freeBuffer();
// mRemote 实际通过ActivityManagerNative.getDefault进行注册的，实际就是ActivityManagerService
static public IActivityManager getDefault()
{
if (gDefault != null) {
//if (Config.LOGV) Log.v(
// "ActivityManager", "returning cur default = " + gDefault);
return gDefault;
}
IBinder b = ServiceManager.getService("activity");
if (Config.LOGV) Log.v(
"ActivityManager", "default service binder = " + b);
gDefault = asInterface(b);
if (Config.LOGV) Log.v(
"ActivityManager", "default service = " + gDefault);
return gDefault;
}
5. 实际调用proxy中的Ontransact方法
public boolean onTransact(int code, Parcel data, Parcel reply, int flags)
throws RemoteException {
switch (code) {
case START_ACTIVITY_TRANSACTION:
{
data.enforceInterface(IActivityManager.descriptor);
IBinder b = data.readStrongBinder();
IApplicationThread app = ApplicationThreadNative.asInterface(b);
Intent intent = Intent.CREATOR.createFromParcel(data);
String resolvedType = data.readString();
Uri[] grantedUriPermissions = data.createTypedArray(Uri.CREATOR);
int grantedMode = data.readInt();
IBinder resultTo = data.readStrongBinder();
String resultWho = data.readString();
int requestCode = data.readInt();
boolean onlyIfNeeded = data.readInt() != 0;
boolean debug = data.readInt() != 0;
int result = startActivity(app, intent, resolvedType,
grantedUriPermissions, grantedMode, resultTo, resultWho,
requestCode, onlyIfNeeded, debug);
reply.writeNoException();
reply.writeInt(result);
return true;
}
6 . startActivity 实际调用ActivityManagerService中的startActivity方法
由于StartActivity太长，拿关键部分分享
synchronized(this) {
final long origId = Binder.clearCallingIdentity();
int res = startActivityLocked(caller, intent, resolvedType,
grantedUriPermissions, grantedMode, aInfo,
resultTo, resultWho, requestCode, -1, -1,
onlyIfNeeded, componentSpecified);
Binder.restoreCallingIdentity(origId);
return res;
}
7. startActivityLocked实际调用ApplicationThread中scheduleLaunchActivity
public final void scheduleLaunchActivity(Intent intent, IBinder token,
ActivityInfo info, Bundle state, List<ResultInfo> pendingResults,
List<Intent> pendingNewIntents, boolean notResumed, boolean isForward) {
ActivityRecord r = new ActivityRecord();（histroyRicord）
r.token = token;
r.intent = intent;
r.activityInfo = info;
r.state = state;
r.pendingResults = pendingResults;
r.pendingIntents = pendingNewIntents;
r.startsNotResumed = notResumed;
r.isForward = isForward;
queueOrSendMessage(H.LAUNCH_ACTIVITY, r);
}
8. queueOrSendMessage 然后发消息给ActivityThread 的Handler
case LAUNCH_ACTIVITY: {
ActivityRecord r = (ActivityRecord)msg.obj;
r.packageInfo = getPackageInfoNoCheck(
r.activityInfo.applicationInfo);
handleLaunchActivity(r);
} break;
具体调用
private final Activity performLaunchActivity(ActivityRecord r) {
// System.out.println("##### [" + System.currentTimeMillis() + "] ActivityThread.performLaunchActivity(" + r + ")");
***
mInstrumentation.callActivityOnCreate(activity, r.state);
***
} catch (SuperNotCalledException e) {
throw e;
} catch (Exception e) {
if (!mInstrumentation.onException(activity, e)) {
throw new RuntimeException(
"Unable to start activity " + component
+ ": " + e.toString(), e);
}
}
return activity;
}
public void startActivity(Intent intent) {
startActivityForResult(intent, -1);
}
2 . 调用Activityd的startActivityForResult方法,Instrumentation class 里面有一个ActivityMonitor 的内部类，用来监控view和system的交互
public void startActivityForResult(Intent intent, int requestCode) {
if (mParent == null) {
Instrumentation.ActivityResult ar =
mInstrumentation.execStartActivity(
this, mMainThread.getApplicationThread(), mToken, this,
intent, requestCode);
if (ar != null) {
mMainThread.sendActivityResult(
mToken, mEmbeddedID, requestCode, ar.getResultCode(),
ar.getResultData());
}
if (requestCode >= 0) {
// If this start is requesting a result, we can avoid making
// the activity visible until the result is received. Setting
// this code during onCreate(Bundle savedInstanceState) or onResume() will keep the
// activity hidden during this time, to avoid flickering.
// This can only be done when a result is requested because
// that guarantees we will get information back when the
// activity is finished, no matter what happens to it.
mStartedActivity = true;
}
} else {
mParent.startActivityFromChild(this, intent, requestCode);
}
}
3. 调用Instrumentation class的 ExecStartActivity：
public ActivityResult execStartActivity(
Context who, IBinder contextThread, IBinder token, Activity target,
Intent intent, int requestCode) {
IApplicationThread whoThread = (IApplicationThread) contextThread;
// 如果找到匹配的Activity，am.mHits++
if (mActivityMonitors != null) {
synchronized (mSync) {
final int N = mActivityMonitors.size();
for (int i=0; i<N; i++) {
final ActivityMonitor am = mActivityMonitors.get(i);
if (am.match(who, null, intent)) {
am.mHits++;
if (am.isBlocking()) {
return requestCode >= 0 ? am.getResult() : null;
}
break;
}
}
}
}
try {
//调用ActivityManagerProxy的startActivity方法
int result = ActivityManagerNative.getDefault()
.startActivity(whoThread, intent,
intent.resolveTypeIfNeeded(who.getContentResolver()),
null, 0, token, target != null ? target.mEmbeddedID : null,
requestCode, false, false);
checkStartActivityResult(result, intent);
} catch (RemoteException e) {
}
return null;
}
4. ActivityManagerProxy 的startActivity的具体实现：
public int startActivity(IApplicationThread caller, Intent intent, String resolvedType, Uri[] grantedUriPermissions, int grantedMode, IBinder resultTo, String resultWho, int requestCode, boolean onlyIfNeeded, boolean debug) throws RemoteException {
// Parcel 本质上把它当成一个Serialize就可以了，只是它是在内存中完成的序列化和反序列化，利用的是连续的内存空间(这里不要作为重点) Parcel data = Parcel.obtain(); Parcel reply = Parcel.obtain(); data.writeInterfaceToken(IActivityManager.descriptor); data.writeStrongBinder(caller != null ? caller.asBinder() : null); intent.writeToParcel(data, 0); data.writeString(resolvedType); data.writeTypedArray(grantedUriPermissions, 0); data.writeInt(grantedMode); data.writeStrongBinder(resultTo); data.writeString(resultWho); data.writeInt(requestCode); data.writeInt(onlyIfNeeded ? 1 : 0); data.writeInt(debug ? 1 : 0);
//具体请参照后面的代码 （这个函数只看到这里就好了！！！） mRemote.transact(START_ACTIVITY_TRANSACTION, data, reply, 0); reply.readException(); int result = reply.readInt(); reply.recycle(); data.recycle(); return result; }
//清除sOwnedPool中parcel对象，返回一个新的parcel
public static Parcel obtain() {
final Parcel[] pool = sOwnedPool;
synchronized (pool) {
Parcel p;
for (int i=0; i<POOL_SIZE; i++) {
p = pool[i];
if (p != null) {
pool[i] = null;
if (DEBUG_RECYCLE) {
p.mStack = new RuntimeException();
}
return p;
}
}
}
return new Parcel(0);
}
// 清除pool中存储parcel,通过jni free刚才分配的内存
public final void recycle() {
if (DEBUG_RECYCLE) mStack = null;
freeBuffer();
final Parcel[] pool = mOwnObject != 0 ? sOwnedPool : sHolderPool;
synchronized (pool) {
for (int i=0; i<POOL_SIZE; i++) {
if (pool[i] == null) {
pool[i] = this;
return;
}
}
}
}
//
private native void freeBuffer();
// mRemote 实际通过ActivityManagerNative.getDefault进行注册的，实际就是ActivityManagerService
static public IActivityManager getDefault()
{
if (gDefault != null) {
//if (Config.LOGV) Log.v(
// "ActivityManager", "returning cur default = " + gDefault);
return gDefault;
}
IBinder b = ServiceManager.getService("activity");
if (Config.LOGV) Log.v(
"ActivityManager", "default service binder = " + b);
gDefault = asInterface(b);
if (Config.LOGV) Log.v(
"ActivityManager", "default service = " + gDefault);
return gDefault;
}
5. 实际调用proxy中的Ontransact方法
public boolean onTransact(int code, Parcel data, Parcel reply, int flags)
throws RemoteException {
switch (code) {
case START_ACTIVITY_TRANSACTION:
{
data.enforceInterface(IActivityManager.descriptor);
IBinder b = data.readStrongBinder();
IApplicationThread app = ApplicationThreadNative.asInterface(b);
Intent intent = Intent.CREATOR.createFromParcel(data);
String resolvedType = data.readString();
Uri[] grantedUriPermissions = data.createTypedArray(Uri.CREATOR);
int grantedMode = data.readInt();
IBinder resultTo = data.readStrongBinder();
String resultWho = data.readString();
int requestCode = data.readInt();
boolean onlyIfNeeded = data.readInt() != 0;
boolean debug = data.readInt() != 0;
int result = startActivity(app, intent, resolvedType,
grantedUriPermissions, grantedMode, resultTo, resultWho,
requestCode, onlyIfNeeded, debug);
reply.writeNoException();
reply.writeInt(result);
return true;
}
6 . startActivity 实际调用ActivityManagerService中的startActivity方法
由于StartActivity太长，拿关键部分分享
synchronized(this) {
final long origId = Binder.clearCallingIdentity();
int res = startActivityLocked(caller, intent, resolvedType,
grantedUriPermissions, grantedMode, aInfo,
resultTo, resultWho, requestCode, -1, -1,
onlyIfNeeded, componentSpecified);
Binder.restoreCallingIdentity(origId);
return res;
}
7. startActivityLocked实际调用ApplicationThread中scheduleLaunchActivity
public final void scheduleLaunchActivity(Intent intent, IBinder token,
ActivityInfo info, Bundle state, List<ResultInfo> pendingResults,
List<Intent> pendingNewIntents, boolean notResumed, boolean isForward) {
ActivityRecord r = new ActivityRecord();（histroyRicord）
r.token = token;
r.intent = intent;
r.activityInfo = info;
r.state = state;
r.pendingResults = pendingResults;
r.pendingIntents = pendingNewIntents;
r.startsNotResumed = notResumed;
r.isForward = isForward;
queueOrSendMessage(H.LAUNCH_ACTIVITY, r);
}
8. queueOrSendMessage 然后发消息给ActivityThread 的Handler
case LAUNCH_ACTIVITY: {
ActivityRecord r = (ActivityRecord)msg.obj;
r.packageInfo = getPackageInfoNoCheck(
r.activityInfo.applicationInfo);
handleLaunchActivity(r);
} break;
具体调用
private final Activity performLaunchActivity(ActivityRecord r) {
// System.out.println("##### [" + System.currentTimeMillis() + "] ActivityThread.performLaunchActivity(" + r + ")");
***
mInstrumentation.callActivityOnCreate(activity, r.state);
***
} catch (SuperNotCalledException e) {
throw e;
} catch (Exception e) {
if (!mInstrumentation.onException(activity, e)) {
throw new RuntimeException(
"Unable to start activity " + component
+ ": " + e.toString(), e);
}
}
return activity;
}
内容来自用户分享和网络整理，不保证内容的准确性，如有侵权内容，可联系管理员处理 
相关文章推荐
- android IntentService实现原理及内部代码分享
- AsyncTask实现原理和内部代码
- IntentService实现原理及内部代码
- 从系统和代码实现角度解析TensorFlow的内部实现原理 | 深度
- StartActivity的内部代码实现原理
- IntentService实现原理及内部代码
- StartActivity的内部代码实现原理
- IntentService实现原理及内部代码
- AsyncTask实现原理和内部代码
- IntentService实现原理及内部代码
- 十三种基于直方图的图像全局二值化算法原理、实现、代码及效果。
- MatConvNet之softmaxloss原理及其代码实现--新版
- Python代码实现双色球原理
- Java NIO原理图文分析及代码实现
- 利用最大熵进行阈值分割从而实现灰度图像的二值化的原理概要及OpenCV代码
- 根据Merge Sort原理, 自己实现的归并排序算法+详细注释+代码(C#,C/C++) [分享]
- 【Java】数组的冒泡排序和选择排序（原理+代码实现）
- JS实现div内部的文字或图片自动循环滚动代码
- Android中悬浮窗口的实现原理和示例代码
- Filter实现原理及内部流程