发表更新Android / 手撸Android源码1 分钟读完 (大约219个字)

基础06-ViewGroup

dispatchTouchEvent

flowchart TD
    A[开始] --> B{过滤事件}
    B -->|true| C{是否ACTION_DOWN}
    B -->|false| D[返回false]
    C -->|true| E[清除TouchTargets，重置TouchState]
    C -->|false| F{111}
    E --> G[调用onInterceptTouchEvent]@{ shape: comment, label: "计算新事件的x，y，传递给child\n若child空，调用super.dispatchTouchEvent" }
    G --> J[处理hover事件]
    J --> F[遍历TouchTarget，调用dispatchTransformedTouchEvent传递event]
    F --> H[如果是up/cancel，重置TouchState]
    H --> I[返回是否handle]

过滤事件

  • 如果this存在flag:FILTER_TOUCHES_WHEN_OBSCURED，event存在flag:FLAG_WINDOW_IS_OBSCURED，就丢掉
  • window被上面的window遮住了，不管这个时间了
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public void setFilterTouchesWhenObscured(boolean enabled) {
    setFlags(enabled ? FILTER_TOUCHES_WHEN_OBSCURED : 0,
            FILTER_TOUCHES_WHEN_OBSCURED);
}

调用view的这个函数，就会设置这个flag

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基础05-Navigation

简介

NavController是中央导航 API。它会跟踪用户访问过的目的地，并允许用户在目的地之间移动。

获取NavController

  • fragment

如果是NavHostFragment

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val navController = this.navController
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基础04-LiveData

LiveData

LiveData的观察者

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fun interface Observer<T> {

    /**
     * Called when the data is changed to [value].
     */
    fun onChanged(value: T)
}
  • 通过onChanged函数分派数据变化

成员

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@SuppressWarnings("WeakerAccess") /* synthetic access */
final Object mDataLock = new Object();
static final int START_VERSION = -1;
@SuppressWarnings("WeakerAccess") /* synthetic access */
static final Object NOT_SET = new Object();

private SafeIterableMap<Observer<? super T>, ObserverWrapper> mObservers =
        new SafeIterableMap<>();

// how many observers are in active state
@SuppressWarnings("WeakerAccess") /* synthetic access */
int mActiveCount = 0;
// to handle active/inactive reentry, we guard with this boolean
private boolean mChangingActiveState;
private volatile Object mData; // 1️⃣：当前的data
// when setData is called, we set the pending data and actual data swap happens on the main
// thread
@SuppressWarnings("WeakerAccess") /* synthetic access */
volatile Object mPendingData = NOT_SET; // 2️⃣：给多线程使用的，在4️⃣mPostValueRunnable中使用
private int mVersion; // 3️⃣：mVersion是数据版本

private boolean mDispatchingValue;
@SuppressWarnings("FieldCanBeLocal")
private boolean mDispatchInvalidated;
private final Runnable mPostValueRunnable = new Runnable() {// 4️⃣mPostValueRunnable，在主线程中将mPendingData设置为当前值
    @SuppressWarnings("unchecked")
    @Override
    public void run() {
        Object newValue;
        synchronized (mDataLock) {
            newValue = mPendingData;
            mPendingData = NOT_SET;
        }
        setValue((T) newValue);
    }
};
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基础02-viewModel

ViewModel简介

在了解ViewModel之前，我们先来了解一下MVC, MVP, MVVM的发展Difference Between MVC, MVP and MVVM Architecture Pattern in Android

ViewModelStoreOwner

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interface ViewModelStoreOwner {

    /**
     * The owned [ViewModelStore]
     */
    val viewModelStore: ViewModelStore
}

ViewModelStore

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基础03-Lifecycle

lifeCycle的Observer

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public interface LifecycleObserver

public interface DefaultLifecycleObserver : LifecycleObserver {
    /**
     * Notifies that `ON_CREATE` event occurred.
     *
     *
     * This method will be called after the [LifecycleOwner]'s `onCreate`
     * method returns.
     *
     * @param owner the component, whose state was changed
     */
    public fun onCreate(owner: LifecycleOwner) {}

    /**
     * Notifies that `ON_START` event occurred.
     *
     *
     * This method will be called after the [LifecycleOwner]'s `onStart` method returns.
     *
     * @param owner the component, whose state was changed
     */
    public fun onStart(owner: LifecycleOwner) {}

    /**
     * Notifies that `ON_RESUME` event occurred.
     *
     *
     * This method will be called after the [LifecycleOwner]'s `onResume`
     * method returns.
     *
     * @param owner the component, whose state was changed
     */
    public fun onResume(owner: LifecycleOwner) {}

    /**
     * Notifies that `ON_PAUSE` event occurred.
     *
     *
     * This method will be called before the [LifecycleOwner]'s `onPause` method
     * is called.
     *
     * @param owner the component, whose state was changed
     */
    public fun onPause(owner: LifecycleOwner) {}

    /**
     * Notifies that `ON_STOP` event occurred.
     *
     *
     * This method will be called before the [LifecycleOwner]'s `onStop` method
     * is called.
     *
     * @param owner the component, whose state was changed
     */
    public fun onStop(owner: LifecycleOwner) {}

    /**
     * Notifies that `ON_DESTROY` event occurred.
     *
     *
     * This method will be called before the [LifecycleOwner]'s `onDestroy` method
     * is called.
     *
     * @param owner the component, whose state was changed
     */
    public fun onDestroy(owner: LifecycleOwner) {}
}

public fun interface LifecycleEventObserver : LifecycleObserver {
    /**
     * Called when a state transition event happens.
     *
     * @param source The source of the event
     * @param event The event
     */
    public fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event)
}
  • 可以看到，我们在使用lifecycle.addObserver()时，可以传入LifecycleEventObserver或DefaultLifecycleObserver，一个通过event获取当前状态，一个通过不同的回调函数获取当前状态

Activity树

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Activity -- AccountAuthenticatorActivity
         |- ActivityGroup -- TabActivity
         |- ExpandableListActivity
         |- LauncherActivity
         |- ListActivity -- PreferenceActivity
         |- NativeActivity
         |- androidx.core.app.ComponentActivity -- androidx.activity.ComponentActivity -- FragmentActivity -- AppCompatActivity
                                                |- PreviewActivity
         |- BootstrapActivity
         |- EmptyActivity
         |- EmptyFloatingActivity

LifecycleOwner

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基础01-Context

大纲

  • Context类
    • 注解
      • 用于标注文件、SharedPreferences、数据库的打开方式的注解
      • 用于标注bindService时，service的flags的注解
      • 用于标注registerReceiver时，receiver的flags的注解
      • 用于标注getService时，servicesName的注解
      • 用于标注createPackageContext、createPackageContextAsUser、createContextAsUser、createApplicationContext时的flags的注解
    • 常量定义
      • 对应上面注解中限制的常量
      • WAL

Context类

Context是抽象类，具体实现在ContextImpl，Application，Service，Activity都直接或间接继承自ContextWrapper，ContextWrapper通过代理的方式调用真正的ContextImpl。

注解

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/** @hide */
@IntDef(flag = true, prefix = { "MODE_" }, value = {
        MODE_PRIVATE,
        MODE_WORLD_READABLE,
        MODE_WORLD_WRITEABLE,
        MODE_APPEND,
})
@Retention(RetentionPolicy.SOURCE)
public @interface FileMode {}

/** @hide */
@IntDef(flag = true, prefix = { "MODE_" }, value = {
        MODE_PRIVATE,
        MODE_WORLD_READABLE,
        MODE_WORLD_WRITEABLE,
        MODE_MULTI_PROCESS,
})
@Retention(RetentionPolicy.SOURCE)
public @interface PreferencesMode {}

/** @hide */
@IntDef(flag = true, prefix = { "MODE_" }, value = {
        MODE_PRIVATE,
        MODE_WORLD_READABLE,
        MODE_WORLD_WRITEABLE,
        MODE_ENABLE_WRITE_AHEAD_LOGGING,
        MODE_NO_LOCALIZED_COLLATORS,
})
@Retention(RetentionPolicy.SOURCE)
public @interface DatabaseMode {}
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