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Android 中读取SD卡文件时抛出NullPointerException错误解决办法

2024-02-22 11:44:03 49

Android中读取SD卡文件时抛出NullPointerException错误解决办法

相关源码：

packagecom.example.musicplayer;

importjava.io.File;
importjava.util.ArrayList;
importjava.util.List;

importandroid.app.Activity;
importandroid.os.Bundle;
importandroid.os.Environment;
importandroid.view.Menu;
importandroid.view.MenuItem;
importandroid.view.View;
importandroid.view.ViewGroup;
importandroid.widget.BaseAdapter;
importandroid.widget.ListView;
importandroid.widget.TextView;
importandroid.widget.Toast;


publicclassMainActivityextendsActivity{

privateListViewlistView;
privatefinalStringpath="/storage/sdcard/mp3/";
privateListmusicList;
privateViewHolderviewHolder;

@Override
protectedvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

listView=(ListView)findViewById(R.id.lv_music);

Toast.makeText(getApplicationContext(),path,Toast.LENGTH_SHORT).show();

initMusic();
}

privatevoidinitMusic(){
Filefile=newFile(path);
File[]files=file.listFiles();
musicList=newArrayList();

for(Filef:files){
if(f.getName().endsWith(".mp3")){
musicList.add(f.getAbsolutePath());
}
}
listView.setAdapter(newMusicListAdapter());
}

privateclassMusicListAdapterextendsBaseAdapter{

@Override
publicintgetCount(){
returnmusicList.size();
}

@Override
publicViewgetView(intposition,ViewconvertView,ViewGroupparent){
Viewview=null;
if(convertView==null){
view=View.inflate(getApplicationContext(),R.layout.activity_music_item,null);
viewHolder=newViewHolder();
viewHolder.musicName=(TextView)view.findViewById(R.id.tv_music_name);
}else{
view=convertView;
}

Stringpath=musicList.get(position);

viewHolder.musicName.setText(path.substring(path.lastIndexOf("/")+1));
returnview;
}

@Override
publicObjectgetItem(intposition){
//TODOAuto-generatedmethodstub
returnnull;
}

@Override
publiclonggetItemId(intposition){
//TODOAuto-generatedmethodstub
return0;
}


}
}

获取SD卡中MP3文件夹下的文件信息时在foreach时抛出NullPointerException，最后发现是没有添加读取SD卡的权限

获取SD卡路径：”/mnt/sdcard/”“/storage/sdcard/”

官方推荐：

Environment.getExternalStorageDirectory.getPath();

该方法获取的路径最后没有'/'

"/mnt/sdcard"
"/storage/sdcard"

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Android 中读取SD卡文件时抛出NullPointerException错误解决办法

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