android按行读取文件内容的几个方法

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public boolean logWeight(Intent batteryChangeIntent) {
            Log.i(TAG, "logBattery");
            if (batteryChangeIntent == null)
                return false;
            try {
                FileWriter out = null;
                if (mWeightLogFile != null) {
                    try {
                        out = new FileWriter(mWeightLogFile, true);
                    }
                    catch (Exception e) {}
                }
                if (out == null) {
                    File root = Environment.getExternalStorageDirectory();
                    if (root == null)
                        throw new Exception("external storage dir not found");
                    mWeightLogFile = new File(root,WeightService.LOGFILEPATH);
                    boolean fileExists = mWeightLogFile.exists();
                    if (!fileExists) {
                        if(!mWeightLogFile.getParentFile().mkdirs()){
                            Toast.makeText(this, "create file failed", Toast.LENGTH_SHORT).show();
                        }