Android入门4--做一个书架（续）

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添加图书布局文件

前面，我们已经做好了一个书架，这里，我们首先为书架添加一些书籍。因为书架本身是Grid View，所以每一本书就是GridView的一个item,那么首先，我们要对这个item进行布局：

添加好之后就会进入到布局设计界面，然后拖一个Text View到主界面上来：

这里可能会有点疑惑，因为我们要做的只是一个item的局部布局，但是预览界面展示的却是整个屏幕。这里，我们忽略其他，只着眼于我们新加的这个线性布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/id_book_item"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:orientation="vertical">

    <TextView
        android:id="@+id/id_book_item_cover"
        android:layout_width="90dp"
        android:layout_height="0dp"
        android:layout_marginTop="85dp"
        android:layout_weight="1"
        android:text="TextView"
        android:textAlignment="center"
        android:textColor="#000" />
</LinearLayout>

需要注意的是，TextView默认加了一个android:layout_weight=”1”，这里需要将android:layout_height设置为0，不然会有警告。

预览效果：

为书架添加模拟数据

这里我添加了32条模拟数据，包含背景图和文字：

private GridView bookShelf;
    private int[] data = {
            R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,
            R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,
            R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,
            R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,
            R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,
            R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,
            R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,
            R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt,R.drawable.cover_txt
    };
    private String[] name={
            "book1","book2","book3","book4",
            "book5","book6","book7","book8",
            "book9","book10","book11","book12",
            "book13","book14","book15","book16",
            "book17","book18","book19","book20",
            "book21","book22","book23","book24",
            "book25","book26","book27","book28",
            "book29","book30","book31","book32"
    };

添加GridView的Adapter

class ShelfAdapter extends BaseAdapter {
        @Override
        public int getCount() {
            return data.length;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            convertView= LayoutInflater.from(getApplicationContext()).inflate(R.layout.layout_book_item, null);
            TextView view=(TextView) convertView.findViewById(R.id.id_book_item_cover);
            if(data.length>position){
                if(position<name.length){
                    view.setText(name[position]);
                }
                view.setBackgroundResource(data[position]);
            }else{
                view.setBackgroundResource(data[0]);
                view.setClickable(false);
                view.setVisibility(View.INVISIBLE);
            }
            return convertView;
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public Object getItem(int position) {
            return position;
        }
    }

这里为了方便使用数据，我将ShelfAdapter嵌套进了MainActivity中。

显示图书项

这里首先我们发现，忘记给bookshelf添加id了，加上：

然后我们就可以写代码了：

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        bookShelf = (GridView) findViewById(R.id.bookshelf);
        ShelfAdapter adapter=new ShelfAdapter();
        bookShelf.setAdapter(adapter);
        bookShelf.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                                    long arg3) {
                // TODO Auto-generated method stub
                if(arg2>=data.length){

                }else{
                    Toast.makeText(getApplicationContext(), ""+ arg2 +arg3, Toast.LENGTH_LONG).show();
                }
            }
        });

    }

调整书架项目布局

为书架视图添加如下属性：

<com.demo.taoguan.BookShelf
        android:id="@+id/bookshelf"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:columnWidth="90dp"
        android:numColumns="auto_fit"
        android:horizontalSpacing="20dp"
        android:verticalSpacing="20dp"
        />

运行效果：