【达内课程】ContentProvider显示图库（上）

1、文件放到如下路径下
mnt——sdcard——Pictures
2、3、可以观察到图库中增加了图片
因为我们读取图片的方式和图库读取图片的方式是相同的，图库中有图片意味着我们也能读取到图片

从Device File Exploer以下路径下导出数据库文件
data——data下的

查看image表会看到我们刚才导入的图片

Image类

public class Image {
    private int id;
    private String data;//path
    private int size;
    private String displayName;
    private long dateTaken;
    private int width;
    private  int height;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getData() {
        return data;
    }

    public void setData(String data) {
        this.data = data;
    }

    public int getSize() {
        return size;
    }

    public void setSize(int size) {
        this.size = size;
    }

    public String getDisplayName() {
        return displayName;
    }

    public void setDisplayName(String displayName) {
        this.displayName = displayName;
    }

    public long getDateTaken() {
        return dateTaken;
    }

    public void setDateTaken(long dateTaken) {
        this.dateTaken = dateTaken;
    }

    public int getWidth() {
        return width;
    }

    public void setWidth(int width) {
        this.width = width;
    }

    public int getHeight() {
        return height;
    }

    public void setHeight(int height) {
        this.height = height;
    }
}

IDao

public interface IDao<T> {
    List<T> getData();
}

MusicDao

import android.content.ContentResolver;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.provider.MediaStore;
import android.util.Log;

import com.example.xx.myapplication2.entity.Image;

import java.util.ArrayList;
import java.util.List;

public class ImageDao implements IDao<Image>{
    private Context context;

    public ImageDao(Context context) {
        this.context = context;
    }

    @Override
    public List<Image> getData() {
        //准备返回值
        List<Image> images = new ArrayList<Image>();
        //准备ContentResolver
        ContentResolver cr = context.getContentResolver();
        //准备Uri
        Uri uri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
        //执行查询，获取Cursor
        //注意和数据库保持一致
        String[] projection = {
          "_id",//0
          "_data",//1
          "_size",//2
          "_display_name",//3
          "datetaken",//4
          "width",//5
          "height",//6
        };
        Cursor c = cr.query(uri, projection, null, null, null);
        //遍历Cursor，读取数据，并封装到返回值
        for(c.moveToFirst();!c.isAfterLast();c.moveToNext()){
            Image image = new Image();
            image.setId(c.getInt(0));
            image.setData(c.getString(1));
            image.setSize(c.getInt(2));
            image.setDisplayName(c.getString(3));
            image.setDateTaken(c.getLong(4));
            image.setWidth(c.getInt(5));
            image.setHeight(c.getInt(6));
            images.add(image);
        }
        //释放资源
        c.close();
        c = null;
        //日志
        for(Image image:images){
            Log.d("Image","id:"+image.getId()+";data:"+image.getData()+";size:"+image.getSize()+
            ";displayname:"+image.getDisplayName()+";dataTaken:"+image.getDateTaken()+";width:"+image.getWidth()+
                    ";height:"+image.getHeight());
        }
        //返回
        return images;
    }
}

万能的BaseAdapter

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import java.util.ArrayList;
import java.util.List;

public class BaseAdapter<T> extends android.widget.BaseAdapter {
    private Context context;
    private List<T> data;
    private LayoutInflater inflater;

    public BaseAdapter(Context context, List<T> data) {
        setContext(context);
        setData(data);
        setInflater();
    }

    public Context getContext() {
        return context;
    }

    public void setContext(Context context) {
        if(context == null){
            throw new IllegalArgumentException("参数Context不允许为null");
        }
        this.context = context;
    }

    public List<T> getData() {
        return data;
    }

    public void setData(List<T> data) {
        if(data == null){
            data = new ArrayList<>();
        }
        this.data = data;
    }

    public LayoutInflater getInflater() {
        return inflater;
    }

    public void setInflater() {
        inflater = LayoutInflater.from(context);
    }

    @Override
    public int getCount() {
        return data.size();
    }

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

    @Override
    public long getItemId(int i) {
        return 0;
    }

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        return view;
    }
}

ImageAdapter

public class ImageAdapter extends BaseAdapter<Image> {
    public ImageAdapter(Context context, List data) {
        super(context, data);
    }

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        ViewHolder viewHolder;
        if(view == null){
            viewHolder = new ViewHolder();
            view = getInflater().inflate(R.layout.item_image,null);
            viewHolder.imageView = (ImageView)view.findViewById(R.id.img_item);
            view.setTag(viewHolder);
        }else {
            viewHolder = (ViewHolder) view.getTag();
        }

        Image image = getData().get(i);
        Bitmap bitmap = BitmapFactory.decodeFile(image.getData());
        viewHolder.imageView.setImageBitmap(bitmap);

        return view;
    }

    class ViewHolder{
        ImageView imageView;
    }
}

MainActivity

public class MainActivity extends Activity implements View.OnClickListener {
    private ListView listView;
    private ImageAdapter imageAdapter;
    private List<Image> imageList;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        listView = findViewById(R.id.lv_images);

        imageList = new ImageDao(this).getData();

        imageAdapter = new ImageAdapter(this,imageList);

        listView.setAdapter(imageAdapter);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {

            default:
                break;
        }
    }
}

activity_main

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".ui.MainActivity">
    <ListView
        android:id="@+id/lv_images"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</LinearLayout>

item_image

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    tools:context=".ui.MainActivity">
    <ImageView
        android:id="@+id/img_item"
        android:layout_width="100dp"
        android:layout_height="100dp" />
</LinearLayout>

AndroidManifest

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

手机打开相应权限

效果

如果想实现一行显示3个

可以把ListView控件改为GridView

 <GridView
        android:id="@+id/lv_images"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:columnWidth="90dp"
        android:horizontalSpacing="9dp"
        android:numColumns="3"
        android:verticalSpacing="10dp"
        />