Android基础——网格视图和适配器,自定义适配器的使用

额外新建一个layout，用来布局ImageView组件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ImageView
        android:layout_width="100dp"
        android:layout_height="75dp"
        android:id="@+id/imageView"
        />
</LinearLayout>

网格视图的布局

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    tools:context=".MainActivity">

<GridView
android:id="@+id/gridView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:numColumns="3">
</GridView>


    </RelativeLayout>

java的调用，使用了适配器SimpleAdapter，将ImageView通过适配器交给GridView

package com.example.myhighuiiii;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.SimpleAdapter;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MainActivity extends AppCompatActivity {

    private int[] picture = new int[]{
            R.drawable.a,R.drawable.b,R.drawable.c,R.drawable.d
    };
    ImageView imageView = null;
    GridView gridView = null;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        gridView = (GridView) findViewById(R.id.gridView);
        //用一个List来存图片对象
        List<Map<String,Object>> listItem = new ArrayList<Map<String, Object>>();
        //把map对象添加到list中
        for(int i=0;i<picture.length;i++){
            Map<String,Object> map = new HashMap<String,Object>();
            map.put("image",picture[i]);
            listItem.add(map);
        }
        //创建simpleAdapter对象
        SimpleAdapter simpleAdapter = new SimpleAdapter(//构造器总共有五个参数
                this,listItem,R.layout.celi,new String[]{"image"},new int[]{R.id.imageView});
        //为网格视图设置适配器
        gridView.setAdapter(simpleAdapter);
    }
}

 自定义适配器使用

layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    tools:context=".MainActivity">

    <GridView
        android:id="@+id/gridView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:numColumns="auto_fit"
        android:gravity="center"
        android:verticalSpacing="5dp"
        android:columnWidth="100dp"
        />


</LinearLayout>

java调用代码

package com.example.myhighuiiii;

import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.content.Context;
import android.media.Image;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridLayout;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.SimpleAdapter;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MainActivity extends Activity {

    private int[] picture = new int[]{
            R.drawable.a,R.drawable.b,R.drawable.c,R.drawable.d
    };
    ImageView imageView = null;
    GridView gridView = null;


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

        //为网格视图设置适配器
        gridView = findViewById(R.id.gridView);
        gridView.setAdapter(new ImageAdpater(MainActivity.this));
    }

    //自定义适配器
    public class ImageAdpater extends BaseAdapter{
        private Context mContext;
        public ImageAdpater(Context context){
            mContext = context;
        }
        @Override//返回图片数组长度
        public int getCount() {
            return picture.length;
        }
        @Override
        public Object getItem(int position) {
            return null;
        }
        @Override
        public long getItemId(int position) {
            return 0;
        }
        //创建一个新的ImageView，用来显示图片，并且将这个图片
        //通过适配器加载到新的ImageView中
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView imageView = null;
            if(convertView==null){
                //如果传过来的值为空,新建一个
                imageView = new ImageView(mContext);
                //设置宽和高
                imageView.setLayoutParams(new GridView.LayoutParams(100,90));
                //设置拉伸方式:保持纵横比
                imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            }
            else {
                //将传过来的值赋给ImageView即可
                imageView = (ImageView) convertView;
            }
            //设置图片资源
            imageView.setImageResource(picture[position]);
            return imageView;
        }
    }
}