android之可摺疊式標題欄(CollapsingToolbarLayout)

1.新建values-v21文件夾，然後新建styles文件

<resources>
    <style name="FruitActivityTheme" parent="AppTheme">
        <item name="android:statusBarColor">@android:color/transparent</item>
    </style>
</resources>

2.在values文件夾中的styles文件中添加

<style name="FruitActivityTheme" parent="AppTheme"/>

3.佈局代碼

<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <android.support.design.widget.AppBarLayout
        android:id="@+id/appBar"
        android:fitsSystemWindows="true"
        android:layout_width="match_parent"
        android:layout_height="250dp">
        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsing_toolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">
            <ImageView
                android:fitsSystemWindows="true"
                android:id="@+id/fruit_image_view"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:scaleType="centerCrop"
                app:layout_collapseMode="parallax"/>
            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:layout_collapseMode="pin"/>
        </android.support.design.widget.CollapsingToolbarLayout>
    </android.support.design.widget.AppBarLayout>
    <android.support.v4.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior">
        <LinearLayout
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <android.support.v7.widget.CardView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginBottom="15dp"
                android:layout_marginLeft="15dp"
                android:layout_marginRight="15dp"
                android:layout_marginTop="35dp"
                app:cardCornerRadius="4dp">
                <TextView
                    android:id="@+id/fruit_content_text"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_margin="10dp"/>
            </android.support.v7.widget.CardView>
        </LinearLayout>
    </android.support.v4.widget.NestedScrollView>
    <android.support.design.widget.FloatingActionButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="16dp"
        android:src="@mipmap/ic_launcher"
        app:layout_anchor="@id/appBar"
        app:layout_anchorGravity="bottom|end"/>
</android.support.design.widget.CoordinatorLayout>

4.代碼

public class FruitActivity extends AppCompatActivity {
    public static final String FRUIT_NAME="fruit_name";
    public static final String FRUIT_IMAGE_ID="fruit_image_id";
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fruit);
        Intent intent=getIntent();
        String fruitName=intent.getStringExtra(FRUIT_NAME);
        int fruitNameId=intent.getIntExtra(FRUIT_IMAGE_ID,0);
        Toolbar toolbar=findViewById(R.id.toolbar);
        CollapsingToolbarLayout collapsingToolbarLayout=findViewById(R.id.collapsing_toolbar);
        ImageView fruitImageView=findViewById(R.id.fruit_image_view);
        TextView fruitContentText=findViewById(R.id.fruit_content_text);
        setSupportActionBar(toolbar);
        ActionBar actionBar=getSupportActionBar();
        if (actionBar!=null){
            actionBar.setDisplayHomeAsUpEnabled(true);
        }
        collapsingToolbarLayout.setTitle(fruitName);
        Glide.with(this).load(fruitNameId).into(fruitImageView);
        String fruitContent=generateFruitContent(fruitName);
        fruitContentText.setText(fruitContent);
    }

    private String generateFruitContent(String fruitName){
        StringBuilder fruitContent=new StringBuilder();
        for (int i=0;i<500;i++){
            fruitContent.append(fruitName);
        }
        return fruitContent.toString();
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()){
            case android.R.id.home:
                finish();
                return true;
        }
        return super.onOptionsItemSelected(item);
    }
}