Android的CollapsingToolbarLayout示例

欢迎来到Android CollapsingToolbarLayout示例。在本教程中，我们将讨论并在我们的应用程序中实现CollapsingToolBarLayout。

Android的CollapsingToolbarLayout

Android的CollapsingToolbarLayout是Toolbar的包装器，它实现了可折叠的应用工具栏。它被设计为AppBarLayout的直接子项使用。这种布局常见于WhatsApp应用的个人资料界面。该布局包括：

• Collapsing Title: The title is larger when the layout is expanded. The text size becomes smaller as the layout is collapsed and scrolled off the screen.
• app:layout_scrollFlags: The scroll flags of this layout is typically set to “scroll|exitUntilCollapsed”.
• app:collapsedTitleGravity: Specifies the gravity of title in the container when collapsed.
• app:contentScrim: This requires specifying a drawable or color value of the CollapsingToolbarLayouts content when it has been scrolled sufficiently off screen eg. ?attr/colorPrimary.
• app:scrimAnimationDuration: Specifies the duration used for scrim visibility animations. This requires an integer value such as “100”.

如果你最近更新了最新的SDK，请在创建新项目时选择滚动活动类型（它包含一个现成的CollapsingToolbarLayout实现）。运行默认的新项目应该会显示如下输出：在本教程中，我们将在默认项目中进行一些更改，例如显示一个ImageView，以及在FAB按钮折叠时显示工具栏等效图标。

Android CollapsingToolbarLayout 示例项目结构

安卓的CollapsingToolbarLayout代码

以下是activity_scrolling.xml文件的内容。

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:app="https://schemas.android.com/apk/res-auto"
    xmlns:tools="https://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="com.Olivia.collapsingtoolbarlayout.ScrollingActivity">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/app_bar"
        android:layout_width="match_parent"
        android:layout_height="@dimen/app_bar_height"
        android:fitsSystemWindows="true"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/toolbar_layout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">


            <ImageView
                android:id="@+id/expandedImage"
                android:layout_width="match_parent"
                android:layout_height="200dp"
                android:scaleType="centerCrop"
                android:src="@drawable/photo"
                app:layout_collapseMode="parallax"
                app:layout_collapseParallaxMultiplier="0.7" />

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:layout_collapseMode="pin"
                app:popupTheme="@style/AppTheme.PopupOverlay" />

        </android.support.design.widget.CollapsingToolbarLayout>
    </android.support.design.widget.AppBarLayout>

    <include layout="@layout/content_scrolling" />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="@dimen/fab_margin"
        app:layout_anchor="@id/app_bar"
        app:layout_anchorGravity="bottom|end"
        app:srcCompat="@android:drawable/ic_dialog_info" />

</android.support.design.widget.CoordinatorLayout>

app:layout_anchor 和 app:layout_anchorGravity 将FAB锚定到AppBarLayout的右下角。注意：content_scrolling.xml在本教程中保持默认设置。menu_scrolling.xml文件如下所示定义。

<menu xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:app="https://schemas.android.com/apk/res-auto"
    xmlns:tools="https://schemas.android.com/tools"
    tools:context="com.Olivia.collapsingtoolbarlayout.ScrollingActivity">
    <item
        android:id="@+id/action_settings"
        android:orderInCategory="100"
        android:title="@string/action_settings"
        app:showAsAction="never" />

    <item
        android:id="@+id/action_info"
        android:orderInCategory="200"
        android:title="info"
        app:showAsAction="ifRoom"
        android:icon="@android:drawable/ic_dialog_info"/>

</menu>

以下是ScrollingActivity.java文件的代码定义:

package com.Olivia.collapsingtoolbarlayout;

import android.os.Bundle;
import android.support.design.widget.AppBarLayout;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;

public class ScrollingActivity extends AppCompatActivity {


    private Menu menu;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_scrolling);
        final Toolbar mToolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(mToolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        AppBarLayout mAppBarLayout = (AppBarLayout) findViewById(R.id.app_bar);
        mAppBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
            boolean isShow = false;
            int scrollRange = -1;

            @Override
            public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
                if (scrollRange == -1) {
                    scrollRange = appBarLayout.getTotalScrollRange();
                }
                if (scrollRange + verticalOffset == 0) {
                    isShow = true;
                    showOption(R.id.action_info);
                } else if (isShow) {
                    isShow = false;
                    hideOption(R.id.action_info);
                }
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        this.menu = menu;
        getMenuInflater().inflate(R.menu.menu_scrolling, menu);
        hideOption(R.id.action_info);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        } else if (id == R.id.action_info) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    private void hideOption(int id) {
        MenuItem item = menu.findItem(id);
        item.setVisible(false);
    }

    private void showOption(int id) {
        MenuItem item = menu.findItem(id);
        item.setVisible(true);
    }
}

在上述代码中，为了知道CollapsingToolbarLayout是折叠还是展开，我们在AppBarLayout实例上添加了一个addOnOffsetChangedListener监听器。根据if else的条件，我们显示或隐藏工具栏信息选项。下面是应用程序的输出效果。这就结束了本教程。你可以从下面的链接中下载Android CollapsingToolbarLayout项目。

下载安卓CollapsingToolbarLayout示例项目