Android四大组件之一：ContentProvider（内容提供者）

Android中还提供了名为ContentProvider（内容提供者），可以向其他应用提供数据，但不常用，除非是同一公司开发的App，可以向不同应用提供数据。虽然为Android的四大组件之一，但用法并不复杂。

建立一个Activity，设置三个Button，分别用于手机相册，Mp3,Mp4的数据的获取。在这里用的是内部类监听方式，不要忘了注册监听。

package com.example.administrator.jreduch09.contentprovider;

import android.database.Cursor;
import android.os.Bundle;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import com.example.administrator.jreduch09.R;

public class ContentActivity extends AppCompatActivity {
    private Button img, mp3, mp4;
    private TextView show;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_content);
        img = (Button) findViewById(R.id.img);
        mp3 = (Button) findViewById(R.id.mp3);
        mp4 = (Button) findViewById(R.id.mp4);
        show = (TextView) findViewById(R.id.show);
        img.setOnClickListener(new MyListerner());
        mp3.setOnClickListener(new MyListerner());
        mp4.setOnClickListener(new MyListerner());
    }

    public class MyListerner implements View.OnClickListener {

        @Override
        public void onClick(View v) {
            int id = v.getId();
            if (id == R.id.img) {
                String str[] = {MediaStore.Images.Media._ID,
                        MediaStore.Images.Media.DISPLAY_NAME,
                        MediaStore.Images.Media.DATA};
                Cursor cursor = getContentResolver()
                        .query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI
                                , str,
                                null, null, null);
                StringBuilder sbd = new StringBuilder();
                while (cursor.moveToNext()) {
                    sbd.append(cursor.getString(0) + ":");
                    sbd.append(cursor.getString(1) + ":");
                    sbd.append(cursor.getString(2) + "\n");
                }
                show.setText(sbd.toString());
            } else if (id == R.id.mp3) {
                String str[] = {MediaStore.Audio.Media._ID,
                        MediaStore.Audio.Media.DISPLAY_NAME,
                        MediaStore.Audio.Media.DATA,
                        MediaStore.Audio.Media.SIZE,
                        MediaStore.Audio.Media.ARTIST,//作者
                        MediaStore.Audio.Media.DURATION,//时常
                        MediaStore.Audio.Media.ALBUM};//专辑
                Cursor cursor = getContentResolver().query(
                        MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
                        str,
                       "duration>?",
                        new String[]{"3000"}, null);
                StringBuilder sbd = new StringBuilder();
                while (cursor.moveToNext()) {
                    sbd.append(cursor.getString(0) + ":");
                    sbd.append(cursor.getString(1) + ":");
                    sbd.append(cursor.getString(2) + ":");
                    sbd.append(cursor.getString(3) + ":");
                    sbd.append(cursor.getString(4) + ":");
                    sbd.append(cursor.getString(5) + ":");
                    sbd.append(cursor.getString(6) + "\n");
                }
                show.setText(sbd.toString());
            } else if (id == R.id.mp4) {
                String str[] = {MediaStore.Video.Media._ID,
                        MediaStore.Video.Media.DISPLAY_NAME,
                        MediaStore.Video.Media.DATA,
                        MediaStore.Video.Media.SIZE};
                Cursor cursor = getContentResolver().query(
                        MediaStore.Video.Media.EXTERNAL_CONTENT_URI,
                        str,
                        null, null, null);
                StringBuilder sbd = new StringBuilder();
                while (cursor.moveToNext()) {
                    sbd.append(cursor.getString(0) + ":");
                    sbd.append(cursor.getString(1) + ":");
                    sbd.append(cursor.getString(2) + ":");
                    sbd.append(cursor.getString(1) + "\n");

                }
                show.setText(sbd.toString());
            }
        }
    }
}