自定义 NavigationView 时StatusBarColor的小问题

一般我们使用 Navigation Menu 的形式为

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
    android:id="@+id/drawer_layout"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">

    <include
        layout="@layout/app_bar_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

    <android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/nav_header_main"
        app:menu="@menu/activity_main_drawer"/>

</android.support.v4.widget.DrawerLayout>

再加上 v21 的主题:

<style name="AppTheme.NoActionBar">
    <item name="windowActionBar">false</item>
    <item name="windowNoTitle">true</item>
    <item name="android:windowDrawsSystemBarBackgrounds">true</item>
    <item name="android:statusBarColor">@android:color/transparent</item>
</style>

这种最标准的形式, 运行的效果就是这样的:

这种效果看起来就好像状态栏浮在 NavigationLayout 之上, 感觉上会好很多

不过, 很多时候, 我们想定义自己的 NavigationMenu, 但是当你换上你自己的 View 替换掉 NavigationView 的时候, 你会发现运行的效果有一点点差池:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
    android:id="@+id/drawer_layout"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">

    <include
        layout="@layout/app_bar_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

    <FrameLayout
        android:layout_gravity="start"
        android:layout_width="250dp"
        android:layout_height="match_parent"
        android:fitsSystemWindows="true"
        android:background="@android:color/holo_blue_bright">

    </FrameLayout>
</android.support.v4.widget.DrawerLayout>

运行效果是这样的:

我们查看 NavigationView 的源代码, 发现它继承自 ScrimInsetsFrameLayout, 再查看 ScrimInsetsFrameLayout 的源代码, 你就会发现, 原来 ScrimInsetsFrameLayout 处理了和系统状态栏相交情况

public ScrimInsetsFrameLayout(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);

    final TypedArray a = context.obtainStyledAttributes(attrs,
            R.styleable.ScrimInsetsFrameLayout, defStyleAttr,
            R.style.Widget_Design_ScrimInsetsFrameLayout);
    /**
     * 这个就是相交区域要画的颜色
     */
    mInsetForeground = a.getDrawable(R.styleable.ScrimInsetsFrameLayout_insetForeground);
    a.recycle();
    setWillNotDraw(true); // No need to draw until the insets are adjusted

    /**
     * 监听和状态栏相交事件
     */
    ViewCompat.setOnApplyWindowInsetsListener(this,
            new android.support.v4.view.OnApplyWindowInsetsListener() {
                @Override
                public WindowInsetsCompat onApplyWindowInsets(View v,
                        WindowInsetsCompat insets) {
                    if (null == mInsets) {
                        mInsets = new Rect();
                    }
                    mInsets.set(insets.getSystemWindowInsetLeft(),
                            insets.getSystemWindowInsetTop(),
                            insets.getSystemWindowInsetRight(),
                            insets.getSystemWindowInsetBottom());
                    onInsetsChanged(mInsets);
                    setWillNotDraw(mInsets.isEmpty() || mInsetForeground == null);
                    ViewCompat.postInvalidateOnAnimation(ScrimInsetsFrameLayout.this);
                    return insets.consumeSystemWindowInsets();
                }
            });
}

@Override
public void draw(@NonNull Canvas canvas) {
    super.draw(canvas);

    int width = getWidth();
    int height = getHeight();
    /**
     * 画出相交部分的颜色
     */
    if (mInsets != null && mInsetForeground != null) {
        int sc = canvas.save();
        canvas.translate(getScrollX(), getScrollY());

        // Top
        mTempRect.set(0, 0, width, mInsets.top);
        mInsetForeground.setBounds(mTempRect);
        mInsetForeground.draw(canvas);

        // Bottom
        mTempRect.set(0, height - mInsets.bottom, width, height);
        mInsetForeground.setBounds(mTempRect);
        mInsetForeground.draw(canvas);

        // Left
        mTempRect.set(0, mInsets.top, mInsets.left, height - mInsets.bottom);
        mInsetForeground.setBounds(mTempRect);
        mInsetForeground.draw(canvas);

        // Right
        mTempRect.set(width - mInsets.right, mInsets.top, width, height - mInsets.bottom);
        mInsetForeground.setBounds(mTempRect);
        mInsetForeground.draw(canvas);

        canvas.restoreToCount(sc);
    }
}

知道了这个原理, 我们可以用这个 ScrimInsetsFrameLayout 放置我们自定义的 Menu View, 并可以用它的属性app:insetForeground定义相交区域的颜色, 或者根据 ScrimInsetsFrameLayout 的代码写一个自己自定义View

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
    android:id="@+id/drawer_layout"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">

    <include
        layout="@layout/app_bar_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

    <android.support.design.internal.ScrimInsetsFrameLayout
        android:layout_gravity="start"
        android:layout_width="250dp"
        android:layout_height="match_parent"
        android:fitsSystemWindows="true"
        android:background="@android:color/holo_blue_bright"
        app:insetForeground="#aaff0000">

    </android.support.design.internal.ScrimInsetsFrameLayout>

</android.support.v4.widget.DrawerLayout>

最后运行的效果是这样的: