如何将数据添加到 android 中的现有 .txt 文件

Question

我正在开发一个读取来自加速度计的数据的应用程序，我想将它们保存在 .txt 文件中，以便我以后可以处理它们。

到目前为止，我已经能够获取读数并仅保存一个读数，据我所知，我总是创建一个新文件来覆盖以前存在的文件。但我想要的是从按下开始按钮到按下停止按钮的那一刻起进行所有测量。

这是我使用的代码：

public class MainActivity extends AppCompatActivity implements SensorEventListener, View.OnClickListener {

private SensorManager mSensorManager;

private Sensor mAccelerometer;
private Button bStart, bStop;
float[] acceleration = new float[3];
private String mString;

MyFile file = new MyFile(this);


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    bStart = (Button)findViewById(R.id.start);
    bStop = (Button)findViewById(R.id.stop);

    mSensorManager=(SensorManager)getSystemService(SENSOR_SERVICE);
    mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

    bStart.setOnClickListener(this);
    bStop.setOnClickListener(this);
    bStart.setEnabled(true);
    bStop.setEnabled(false);
}

@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {}

public final void onSensorChanged(SensorEvent event){
    if(event.sensor.getType() ==  Sensor.TYPE_ACCELEROMETER){
        acceleration[0] = event.values[0];
        acceleration[1] = event.values[1];
        acceleration[2] = event.values[2];
        TextView mTextview1 = (TextView) findViewById(R.id.textView1);
        TextView mTextview2 = (TextView) findViewById(R.id.textView2);
        TextView mTextview3 = (TextView) findViewById(R.id.textView3);
        mTextview1.setText("X:"+String.valueOf( acceleration[0]));
        mTextview2.setText("Y:"+String.valueOf( acceleration[1]));
        mTextview3.setText("Z:"+String.valueOf( acceleration[2]));

        file.writeToSD(acceleration[0] + "," +acceleration[1] + "," +acceleration[2] + "\n");
    }
}

@Override
public void onClick(View v) {
    switch(v.getId()){
        case R.id.start:
            bStart.setEnabled(false);
            bStop.setEnabled(true);
            mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);
            break;
        case R.id.stop:
            bStart.setEnabled(true);
            bStop.setEnabled(false);
            mSensorManager.unregisterListener(this);
            break;
    }
}

}

和 MyFile Class，完成工作的地方如下：

public class MyFile {

String TAG = "MyFile";
Context context;

public MyFile(Context context) {
    this.context = context;
}

public Boolean writeToSD(String text) {
    Boolean write_successful = false;
    File root = null;
    try {
        // check for SDcard
        root = Environment.getExternalStorageDirectory();
        Log.i(TAG, "path.." + root.getAbsolutePath());

        //check sdcard permission
        if (root.canWrite()) {
            File fileDir = new File(root.getAbsolutePath());
            fileDir.mkdirs();

            File file = new File(fileDir, "samplefile.txt");
            FileWriter filewriter = new FileWriter(file);
            BufferedWriter out = new BufferedWriter(filewriter);
            out.append(text);
            out.flush();
            out.close();
            write_successful = true;
        }
    } catch (IOException e) {
       e.printStackTrace();
        write_successful = false;
    }
    return write_successful;
}

}

我的另一个问题是为什么我无法将.txt文件存储在sdcard中，而是保存在内部存储器中。

感谢您的宝贵时间和帮助

Answer 1

试试这个代码。将 FileWriter 的第二个参数设置为 true。因此，您可以附加现有文件

 File file = new File("Hello.txt");    
 file.createNewFile();    
 FileWriter writer = new FileWriter(file,true); 
 writer.write("Writes the content to the file"); 
 writer.flush();
 writer.close();

如何将数据添加到 android 中的现有 .txt 文件

How to add data to an existing .txt file in android

android

file-io

accelerometer