Android第三次作业

1.实现功能： 实现点击列表播放音乐，点击按钮播放上一首，下一首及暂停的功能 ；显示播放列表 ；选中歌曲高亮显示

2.界面截图：

3.关键代码：

//获取音乐信息并用hashmap保存
 if(ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){
            ActivityCompat.requestPermissions(MainActivity.this,new String[]{
                    Manifest.permission.WRITE_EXTERNAL_STORAGE},1);
        }
        try {
            Context context = this;
            Cursor cursor = context.getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,  null ,
                    null ,  null , MediaStore.Audio.Media.DEFAULT_SORT_ORDER);

            while (cursor.moveToNext()){
                String musicNmae = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DISPLAY_NAME));
                String musicPath = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA));
                musicInfo.put(musicNmae,musicPath);
            }

        }catch (Exception e){
            Toast.makeText(getApplicationContext(), "获取音乐失败", Toast.LENGTH_SHORT).show();;
        }

        Iterator entries = musicInfo.entrySet().iterator();
        while(entries.hasNext()){
            Map.Entry entry = (Map.Entry) entries.next();
            list.add((String)entry.getKey()) ;
        }

//设置ListView样式并添加监视
ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1 , list){
            public View getView(int position, View convertView, ViewGroup parent) {
                View view = super.getView(position, convertView, parent);
                TextView text = (TextView) view.findViewById(android.R.id.text1);
                text.setTextColor(Color.WHITE);
                return view;
            }

        };
        listView = (ListView) findViewById(R.id.list_view);
        listView.setAdapter(adapter);
        listView.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView parent, View view, int position, long id) {
                playingMusicPath = (String)musicInfo.get(list.get(position));
                playingPosition = position;
                changePlaying(playingPosition);

                try {
                    mediaPlayer.reset();
                    mediaPlayer.setDataSource(playingMusicPath);
                    mediaPlayer.prepare();
                    mediaPlayer.start();
                } catch (Exception e) {
                }
            }

        });

//为上一首、暂停、下一首按键添加监视
 play.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (playingMusicPath.isEmpty())
                    Toast.makeText(getApplicationContext(), "请先选择音乐", Toast.LENGTH_SHORT).show();
                else{
                    if(mediaPlayer.isPlaying()) {
                        mediaPlayer.pause();
                        play.setImageResource(R.drawable.play);
                    } else{
                        mediaPlayer.start();
                        play.setImageResource(R.drawable.pause);
                    }
                }
            }
        });


        previous.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if((playingPosition - 1 ) < 0){
                    playingPosition = (list.size() - 1);
                    changePlaying(playingPosition);
                } else{
                    playingPosition -= 1;
                    changePlaying(playingPosition);
                }

                play.setImageResource(R.drawable.pause);
            }
        });

        next.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(playingPosition  + 1 > (list.size() - 1)){
                    playingPosition = 0;
                    changePlaying(playingPosition);
                }else{
                    playingPosition += 1;
                    changePlaying(playingPosition);
                }

                play.setImageResource(R.drawable.pause);
            }
        });

4.代码链接：https://git.coding.net/XL_1600802098/MusicPlayer.git

5.APP链接：https://coding.net/s/b83354ac-e185-4a2d-a472-d738e339ae9b