Android学习笔记_59_清除sdcard缓存

　　对于手机来说，每个软件在安装时，都会在sdcard上创建一个目录，用于缓存文件。市场上针对这些软件，统一了它的sdcard上的目录，将缓存目录存放到数据库中。如果要清理，可以根据当前应用包的名称，到数据库去查询缓存路径，如果

到再进行递归删除它下的文件。

public class DemoActivity extends Activity {
    private TextView tv;
    private ProgressBar pb;
    private SQLiteDatabase db;
    private Handler handler = new Handler(){

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            String text = (String) msg.obj;
            tv.setText(text);
        }

    };

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        tv = (TextView) this.findViewById(R.id.tv);
        pb = (ProgressBar) this.findViewById(R.id.progressBar1);

        // 判断手机内存里面是否有数据库存在
        File file = new File("/data/data/cn.itcast.clear/files/clearpath.db");
        if (!file.exists()) {
            copyfile();
        }
 // 文件写到哪里了?
            // data/data/cn.itcast.clear/files/name

    }

    public void start(View view) {
        db = SQLiteDatabase.openDatabase("/data/data/cn.itcast.clear/files/clearpath.db", null, SQLiteDatabase.OPEN_READONLY);
        new Thread(){
            @Override
            public void run() {
                List<PackageInfo> packinfos =    getPackageManager().getInstalledPackages(0);
                pb.setMax(packinfos.size());// 设置进度条的最大条目个数
                int total=0;
                for(PackageInfo info : packinfos){
                    String packname = info.packageName;
                    Cursor curosr = db.rawQuery("select filepath from softdetail where apkname=?", new String[]{packname});
                    if(curosr.moveToFirst()){
                        String path = curosr.getString(0);
                        System.out.println("清除"+packname+"sd卡缓存"+path);
                        File file = new File(Environment.getExternalStorageDirectory(),path);
                        deleteDir(file);
                        try {
                            sleep(500);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                    total++;
                    pb.setProgress(total);
                    curosr.close();
                    Message msg = Message.obtain();
                    msg.obj = "清除"+packname;
                    handler.sendMessage(msg);
                }

                Message msg = Message.obtain();
                msg.obj = "清除完毕";
                handler.sendMessage(msg);
                db.close();
            }

        }.start();
    }

    private void copyfile() {

        try {
            InputStream is = getClass().getClassLoader().getResourceAsStream(
                    "clearpath.db");
           OutputStream fos =    this.openFileOutput("clearpath.db", MODE_PRIVATE);
            byte[] buffer = new byte[1024];
            int len = 0;

            while ((len = is.read(buffer)) != -1) {
                fos.write(buffer, 0, len);
            }
            fos.flush();
            fos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
　　//递归删除缓存文件夹下的文件
    private void deleteDir(File file){
        if(file.isDirectory()){
            File[] files = file.listFiles();
            for(int i=0;i<files.length;i++){
                deleteDir(file);
            }
        }else{
            file.delete();
        }

    }
}