開啟頁面自動登入並回來-攔截器(升級版)

安卓開發 · 發表 2018-10-27 23:22:42

摘要：之前寫過一篇文章，講解如何解耦頁面跳轉和自動登入，至於思想想必看過那篇文章的人都懂了，簡單說就是很多地方都會跳轉某個頁面（稱呼為A頁面），但A頁面需要登入後才能載入資料，我們不希望發起跳轉的頁面負責登入判斷和登入的工作，即：登入判斷和跳轉登入應該是A頁面自己的份內工作。 ...

之前寫過一篇文章，講解如何 ofollow,noindex">解耦頁面跳轉和自動登入，至於思想想必看過那篇文章的人都懂了，簡單說就是很多地方都會跳轉某個頁面（稱呼為A頁面），但A頁面需要登入後才能載入資料，我們不希望發起跳轉的頁面負責登入判斷和登入的工作，即：登入判斷和跳轉登入應該是A頁面自己的份內工作。

inteceptor.png

只是，之前的實現有程式碼侵入性，需要一個讓A頁面繼承一個叫 InterceptorActivity 的頁面（負責註解解析和校驗），又恐怕大家專案都已經有了一個所謂的BaseActivity，逼不得已要改動此BaseActivity讓其繼承 InterceptorActivity , 很明顯這是有侵入性的。

新的實現方案是建立一個無UI的Fragment的代理，它負責做真正的 startActivityForResult() ，隨後的activityResult通過它們之間的callback傳給建立無UI Fragment的Activity或者Fragment，這原理其實很簡單。因此，我們又有了另外一個發現：簡化 startActivityForResult() , 即：以掛回調的方式處理activityResult。

其實，Android 6.0許可權請求的API跟 startActivityForResult() 及其類似（ requestPermissions (String[] permissions, int requestCode) 和 onRequestPermissionsResult (int requestCode, String permissions[], int[] grantResults) ），在此之前也寫過篇文章如何通過此原理簡化了 Android 6.0許可權的請求。

如下演示瞭如何在Activity、Fragment中開啟需要先登入的訂單詳情頁，以及不僅要登入還要授權的管理員頁面，還有在Activity和Fragment中以掛回調的方式startActivityForResult()接收activityResult:

activity_result.gif

1. Activity攔截器新的接入方式：

// 1. open OrderDetailActivity
Intent intent = new Intent(context, OrderDetailActivity.class);
startActivity(intent);

// 2. implementation of OrderDetailActivity
@InterceptWith(LoginInterceptor.class)
public class OrderDetailActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_order_detail);

ActivityResult result = new ActivityResult(this);
result.intercept(new OnInterceptResult(this) {

/**
* init data or load data from http and so on after all interceptors is validated.
*/
@Override
public void invoke() {
TextView imageView = findViewById(R.id.contentView);
imageView.setText("This Is the Order Detail Page");
}
});
}
}

ActivityResult 物件的建立可以在Activity也可在Fragment。

如果需要多個校驗攔截，配置方式跟以前一樣（當所有Interceptor都校驗通過才會觸發 invoke() 執行）：

@InterceptWith({LoginInterceptor.class, PermissionInterceptor.class})
public class AdminActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_admin_activity);

ActivityResult activityResult = new ActivityResult(this);
activityResult.intercept(new OnInterceptResult(this) {
@Override
public void invoke() {
TextView textView = findViewById(R.id.contentView);
textView.setText("This The Admin Manager page");
}
});
}
}

2. 以掛回調的方式接收activityResult：

Intent intent = new Intent(Intent.ACTION_PICK, ContactsContract.CommonDataKinds.Phone.CONTENT_URI);
ActivityResult activityResult = new ActivityResult(this);
activityResult.startActivityForResult(intent, new OnResultCallback() {

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
if (resultCode == Activity.RESULT_OK) {
String phoneNum = Util.resolvePhoneNumber(getApplicationContext(), data.getData());
Toast.makeText(MainActivity.this, "phone number: " + phoneNum, Toast.LENGTH_SHORT).show();
}
}
});

3. 如何實現之ActivityResult:

public class ActivityResult {
private static final String TAG = ActivityResult.class.getSimpleName();

private List<Interceptor> mInterceptors = new ArrayList<>();
private Lazy<ResultFragment> mResultFragment;

public ActivityResult(FragmentActivity activity) {
mResultFragment = getLazySingleton(activity.getSupportFragmentManager());
findInterceptors(activity);
}

public ActivityResult(Fragment fragment) {
mResultFragment = getLazySingleton(fragment.getChildFragmentManager());
findInterceptors(fragment);
}

/**
* Convenient method to start activity for result.
*/
public void startActivityForResult(Intent intent, OnResultCallback callback) {
mResultFragment.get().startActivityForResult(intent, callback);
}

/**
* Check if interceptors specified with annotation {@link InterceptWith} are valid or not.
*/
public void intercept(final OnInterceptResult callback) {
mResultFragment.get().intercept(new OnResultCallback() {
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
for (Interceptor interceptor : mInterceptors) {
if (interceptor.getRequestCode() == requestCode) {
if (resultCode == Activity.RESULT_OK) {
verifyInterceptors(callback);
break;
} else if (resultCode == Activity.RESULT_CANCELED) {
callback.finishSelf();
break;
}
}
}
}
});

// verify interceptors
if (!mInterceptors.isEmpty()) {
verifyInterceptors(callback);
}
}

private void findInterceptors(Object object) {
mInterceptors.clear();
InterceptWith annotation = object.getClass().getAnnotation(InterceptWith.class);
if (annotation != null) {
Class<? extends Interceptor>[] classes = annotation.value();
for (Class<? extends Interceptor> clazz : classes) {
try {
mInterceptors.add(clazz.newInstance());
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}
}

private void verifyInterceptors(OnInterceptResult callback) {
if (mInterceptors.isEmpty()) {
return;
}

for (int i = 0; i < mInterceptors.size(); i++) {
Interceptor interceptor = mInterceptors.get(i);
if (interceptor.isValid(mResultFragment.get().getContext())) {
if (i == mInterceptors.size() - 1) {
callback.invoke();
break;
}
} else {
interceptor.process(mResultFragment.get());
break;
}
}
}

@NonNull
private Lazy<ResultFragment> getLazySingleton(@NonNull final FragmentManager fragmentManager) {
return new Lazy<ResultFragment>() {
private ResultFragment permissionsFragment;

@Override
public synchronized ResultFragment get() {
if (permissionsFragment == null) {
permissionsFragment = getPermissionsFragment(fragmentManager);
permissionsFragment.setLogging(true);
}
return permissionsFragment;
}
};
}

private ResultFragment getPermissionsFragment(@NonNull final FragmentManager fragmentManager) {
ResultFragment permissionsFragment = (ResultFragment) fragmentManager.findFragmentByTag(TAG);
boolean isNewInstance = permissionsFragment == null;
if (isNewInstance) {
permissionsFragment = new ResultFragment();
fragmentManager
.beginTransaction()
.add(permissionsFragment, TAG)
.commitNow();
}
return permissionsFragment;
}

@FunctionalInterface
interface Lazy<V> {
V get();
}
}

兩個建構函式使得可以在Activity和Fragment裡工作，瞭解之前文章的朋友會發現解析註解的工作現在放在了 ActivityResult 裡了，不再依賴Override Activity了。 ActivityResult 的作用就是建立 ResultFragment 並委託其 startActivityForResult() , 隨後的結果返回通過 OnResultCallback 或者 OnInterceptResult 傳遞出去。

4. 如何實現之ResultFragment:

/**
 * It's a interceptor fragment and it is used to startActivityForResult()
 * and pass activity result to its observer via callback.
 */
public class ResultFragment extends Fragment {
private static final String TAG = "PermissionsFragment";
public static final int REQUEST_CODE = 9998;

private OnResultCallback mOnResultCallback;
private boolean mLogging;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
}

void startActivityForResult(Intent intent, OnResultCallback callback) {
startActivityForResult(intent, REQUEST_CODE);
mOnResultCallback = callback;
}

void intercept(OnResultCallback callback) {
mOnResultCallback = callback;
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
mOnResultCallback.onActivityResult(requestCode, resultCode, data);
}
}

ResultFragment的實現非常簡單，它就是一個普通Fragment，負責把activityResult通過callback回傳給它的建立者。

完整實現可以參考這裡

開啟頁面自動登入並回來-攔截器(升級版)

1. Activity攔截器新的接入方式：

2. 以掛回調的方式接收activityResult：

3. 如何實現之ActivityResult:

4. 如何實現之ResultFragment:

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