ActionBar的Overlay模式如何不遮盖顶部内容的问题

泡在网上的日子 / 文 发表于2014-09-30 12:54 次阅读 ActionBar

关于actionbar的overlay模式请参考 如何让android的actionbar浮动且透明 一文。这篇文章讲的是如何在这种模式下让actionbar不遮住顶部的内容。

这一般是这样的场景,在一个ListView显示图片的界面中,当ListView向下滑动的时候,actionbar是是浮动在GridView上面一层的,但是当ListView滚动到顶部,顶部的内容是完全显示出来的,当然这种情况一般ActionBar我们会做成透明效果。

其实很多人都能想到的是,将ListView加上一个高度和actionbar的高度相同的header不就行了吗?

但是,难点是如何得到actionbar的高度。

actionbar的高度其实是在android系统主题的资源文件中定义的,如果你没有主动去修改actionbar的高度,那么可以通过下面的代码来获取:

TypedArray actionbarSizeTypedArray = getActivity().obtainStyledAttributes(new int[] {
        android.R.attr.actionBarSize
});
float h = actionbarSizeTypedArray.getDimension(0, 0);

但是这种方式并不太规范,而且在android4.4之后,statusbar所在的区域也是可以显示内容的,这时你还得去计算statusbar的高度。

其实FrameLayout 中boolean fitSystemWindows(Rect insets)方法的insets参数就包含了非内容区域的高度。fitSystemWindows会在加载的时候被调用,如果我们在ListView重写fitSystemWindows不就可以知道该给ListView添加多高的HeaderView了吗?

但是一般我们不希望这样用ListView,因为使用重写的ListView的几率实在太大了(下拉刷新ListView等),而采取另外的方法,把ListView和一个重写了fitSystemWindows方法的FrameLayout放在同一个FrameLayout中,然后通过回调的方式来通知ListView已经获取到了actionbar(或者+statusbar)的高度了。

我们将这个实现了fitSystemWindows方法的FrameLayout命名为:DrawInsetsFrameLayout

代码如下:

/*
 * Copyright 2014 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.example.drawinsetsframelayoutdemo;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.widget.FrameLayout;
/**
 * A layout that draws something in the insets passed to {@link #fitSystemWindows(Rect)}, i.e. the area above UI chrome
 * (status and navigation bars, overlay action bars).
 */
public class DrawInsetsFrameLayout extends FrameLayout {
    private Drawable mInsetBackground;
    private Rect mInsets;
    private Rect mTempRect = new Rect();
    private OnInsetsCallback mOnInsetsCallback;
    public DrawInsetsFrameLayout(Context context) {
        super(context);
        init(context, null, 0);
    }
    public DrawInsetsFrameLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context, attrs, 0);
    }
    public DrawInsetsFrameLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init(context, attrs, defStyle);
    }
    private void init(Context context, AttributeSet attrs, int defStyle) {
        final TypedArray a = context.obtainStyledAttributes(attrs,
                R.styleable.DrawInsetsFrameLayout, defStyle, 0);
        if (a == null) {
            return;
        }
        mInsetBackground = a.getDrawable(R.styleable.DrawInsetsFrameLayout_insetBackground);
        a.recycle();
        setWillNotDraw(true);
    }
    @Override
    protected boolean fitSystemWindows(Rect insets) {
        mInsets = new Rect(insets);
        setWillNotDraw(mInsetBackground == null);
        postInvalidateOnAnimation();
        if (mOnInsetsCallback != null) {
            mOnInsetsCallback.onInsetsChanged(insets);
        }
        return true; // consume insets
    }
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        int width = getWidth();
        int height = getHeight();
        if (mInsets != null && mInsetBackground != null) {
            // Top
            mTempRect.set(0, 0, width, mInsets.top);
            mInsetBackground.setBounds(mTempRect);
            mInsetBackground.draw(canvas);
            // Bottom
            mTempRect.set(0, height - mInsets.bottom, width, height);
            mInsetBackground.setBounds(mTempRect);
            mInsetBackground.draw(canvas);
            // Left
            mTempRect.set(0, mInsets.top, mInsets.left, height - mInsets.bottom);
            mInsetBackground.setBounds(mTempRect);
            mInsetBackground.draw(canvas);
            // Right
            mTempRect.set(width - mInsets.right, mInsets.top, width, height - mInsets.bottom);
            mInsetBackground.setBounds(mTempRect);
            mInsetBackground.draw(canvas);
        }
    }
    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        if (mInsetBackground != null) {
            mInsetBackground.setCallback(this);
        }
    }
    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        if (mInsetBackground != null) {
            mInsetBackground.setCallback(null);
        }
    }
    /**
     * Allows the calling container to specify a callback for custom processing when insets change (i.e. when
     * {@link #fitSystemWindows(Rect)} is called. This is useful for setting padding on UI elements based on
     * UI chrome insets (e.g. a Google Map or a ListView). When using with ListView or GridView, remember to set
     * clipToPadding to false.
     */
    public void setOnInsetsCallback(OnInsetsCallback onInsetsCallback) {
        mOnInsetsCallback = onInsetsCallback;
    }
    public static interface OnInsetsCallback {
        public void onInsetsChanged(Rect insets);
    }
}

其中最主要的就是fitSystemWindows方法,其他的不过是绘制DrawInsetsFrameLayout在actionbar部分的显示颜色而已。

如何使用DrawInsetsFrameLayout呢?

package com.example.drawinsetsframelayoutdemo;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import android.app.Activity;
import android.graphics.Rect;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.Window;
import android.view.ViewGroup.LayoutParams;
import android.widget.AbsListView;
import android.widget.ListView;
import android.widget.SimpleAdapter;
public class MainActivity extends Activity {
    private ListView listView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView= (ListView) findViewById(R.id.listview);
        String[] from = { "Text", "Button" };
        int[] to = { R.id.text, R.id.button };
        List<Map<String, ?>> list = new ArrayList<Map<String, ?>>();
        for (int i = 0; i < 103; i++) {
            Map<String, String> m = new HashMap<String, String>();
            m.put("Text", "Text" + i);
            m.put("Button", "Button" + i);
            list.add(m);
        }
        SimpleAdapter adapter = new SimpleAdapter(this, list, R.layout.listitem, from, to);
        listView.setAdapter(adapter);
                                                                                                                                                                                                                         
        DrawInsetsFrameLayout drawInsetsFrameLayout = (DrawInsetsFrameLayout) findViewById(R.id.my_draw_insets_layout);
        drawInsetsFrameLayout.setOnInsetsCallback(new DrawInsetsFrameLayout.OnInsetsCallback() {
            @Override
            public void onInsetsChanged(Rect insets) {
                // Update the map padding (inset the compass, zoom buttons, attribution, etc.)
                Log.i("", "insets.top = " + insets.top);
                View headerView = new View(MainActivity.this);
                AbsListView.LayoutParams params = new AbsListView.LayoutParams(LayoutParams.FILL_PARENT, insets.top);
                                                                                                                                                                                                                                
                headerView.setLayoutParams(params);
                headerView.setBackgroundColor(0x33000000); 
                listView.addHeaderView(headerView);
            }
        });
    }
                                                                                                                                                                                                                
}

设置actionbar风格的xml文件:

<!-- Application theme. -->
<style name="AppTheme" parent="AppBaseTheme">
    <item name="android:actionBarStyle">@style/TranslucentActionBar</item>
    <item name="android:windowActionBarOverlay">true</item>
    <item name="android:windowTranslucentStatus">true</item>
</style>
<style name="TranslucentActionBar" parent="android:Widget.Holo.Light.ActionBar.Solid.Inverse">
    <item name="android:background">@null</item>
</style>

其中TranslucentActionBar是为DrawInsetsFrameLayout自定义的一个属性,而activity的actionbar和statusbar在这里我们都是设置成了浮动模式的,注意<item name="android:windowTranslucentStatus">true</item>

最后是布局代码:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:yourapp="http://schemas.android.com/apk/res-auto"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
    />
    <com.example.drawinsetsframelayoutdemo.DrawInsetsFrameLayout
        android:id="@+id/my_draw_insets_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        yourapp:insetBackground="#9000" />
</FrameLayout>

效果图:

-----


完整的demo代码在这里下载:http://download.csdn.net/detail/jianghejie123/7992853



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