android - getArgument() 返回 NULL

Question

在下面的代码中，我尝试将传感器值从 Frag1 传递到 Frag2通过 mainActivity。 Frag1 实现了 sensorEvenListener，在 Frag1 的 onResume 中，我通过 sendValues 将值传递给 mainActivtiy。 onSendValues(getAccX(), getAccY(), getAccZ()); sendValues 是在 中实现的名为 onSendListener 的接口(interface)对象>mainActivity.

在 MainActivity 中，我使用

将数据传递给 Frag2

@Override
public void onSendValues(float x, float y, float z) {
    // TODO Auto-generated method stub
    Bundle b = new Bundle();
    b.putFloat("x", x);
    b.putFloat("y", y);
    b.putFloat("z", z);

    Frag2 frag2 = new Frag2();
    frag2.setArguments(b);
}

如下代码所示。

问题是，当我检查发送到 Frag2 的包是否为 null 时，我发现它是 null，为什么它是 null？

请找到下面发布的代码

** 主要 Activity **:

public class MainActivity extends Activity implements onSendListener {

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

/**
 * to send values from frag1 to frag2 through mainActivity. use bundle.
 */
@Override
public void onSendValues(float x, float y, float z) {
    // TODO Auto-generated method stub
    Bundle b = new Bundle();
    b.putFloat("x", x);
    b.putFloat("y", y);
    b.putFloat("z", z);

    Frag2 frag2 = new Frag2();
    frag2.setArguments(b);
}
}

** fragment 1 **:

public class Frag1 extends Fragment implements SensorEventListener {

private SensorManager sensorManager;
TextView tvAccX;
TextView tvAccY;
TextView tvAccZ;

private float x = 0.0f;
private float y = 0.0f;
private float z = 0.0f;

private void setAccX(float x) {
    this.x = x;
}
private float getAccX() {
    return this.x;
}

private void setAccY(float y) {
    this.y = y;
}
private float getAccY() {
    return this.y;
}

private void setAccZ(float z) {
    this.z = z;
}
private float getAccZ() {
    return this.z;
}

Button btnSend;
onSendListener sendValues;

@Override
public void onAttach(Activity activity) {
    // TODO Auto-generated method stub
    super.onAttach(activity);

    sendValues = (onSendListener) activity;
    sensorManager = (SensorManager) getActivity().getSystemService(Context.SENSOR_SERVICE);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    View view = inflater.inflate(R.layout.frag_1, container, false);

    tvAccX = (TextView) view.findViewById(R.id.tv_accX_value);
    tvAccY = (TextView) view.findViewById(R.id.tv_accY_value);
    tvAccZ = (TextView) view.findViewById(R.id.tv_accZ_value);
    btnSend = (Button) view.findViewById(R.id.btn_send);

    return view;
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onViewCreated(view, savedInstanceState);


}

@Override
public void onSensorChanged(SensorEvent event) {
    // TODO Auto-generated method stub
    switch (event.sensor.getType()) {
    case Sensor.TYPE_ACCELEROMETER:
        showAccReadings(event);
        break;

    default:
        break;
    }
}

private void showAccReadings(SensorEvent event) {
    // TODO Auto-generated method stub
    float[] values = event.values;

    float x = values[0];
    float y = values[1];
    float z = values[2];

    setAccX(x);
    setAccY(y);
    setAccZ(z);

    tvAccX.setText(String.valueOf(x));
    tvAccY.setText(String.valueOf(y));
    tvAccZ.setText(String.valueOf(z));
}

@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
    // TODO Auto-generated method stub

}

@Override
public void onResume() {
    // TODO Auto-generated method stub
    super.onResume();

    Sensor accSensor = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
    sensorManager.registerListener(this, accSensor, sensorManager.SENSOR_DELAY_FASTEST);

    btnSend.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            sendValues.onSendValues(getAccX(), getAccY(), getAccZ());
        }
    });
}

@Override
public void onPause() {
    // TODO Auto-generated method stub
    super.onPause();
    sensorManager.unregisterListener(this);
}

}

** fragment 2 **:

public class Frag2 extends Fragment {

float x;
float y;
float z;

TextView tvX;
TextView tvY;
TextView tvZ;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    // TODO Auto-generated method stub

    x = getArguments().getFloat("x");
    y = getArguments().getFloat("y");
    z = getArguments().getFloat("z");

    View view = inflater.inflate(R.layout.frag_2, container, false);

    tvX = (TextView) view.findViewById(R.id.tv_accX2_label);
    tvY = (TextView) view.findViewById(R.id.tv_accY2_label);
    tvZ = (TextView) view.findViewById(R.id.tv_accZ2_label);

    return view;
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onViewCreated(view, savedInstanceState);

    if (getArguments() != null) {
        Log.d("Frag2", "getArgument() is not NULL");
        x = getArguments().getFloat("x");
        y = getArguments().getFloat("y");
        z = getArguments().getFloat("z");
    } else {
        Log.d("Frag2", "getArgument() is NULL");
    }

    tvX.setText(String.valueOf(x));
    tvY.setText(String.valueOf(y));
    tvZ.setText(String.valueOf(z));
}
}

** mainActivity.xml**:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="${relativePackage}.${activityClass}">

<fragment
    android:name="com.example.fragmentcommunication_00.Frag1"
    android:id="@+id/frag_1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"/>

<fragment
    android:name="com.example.fragmentcommunication_00.Frag2"
    android:id="@+id/frag_2"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="50dp"
    android:layout_centerHorizontal="true"
    android:layout_below="@id/frag_1"/>

Answer 1

您的代码中有两个 Frag2。

第一个是在 mainActivity.xml 的膨胀期间创建的，并且在执行其 onCreateView 或 onViewCreated 方法时没有参数传递给它。

第二个在您的代码中实例化如下:

Frag2 frag2 = new Frag2();
frag2.setArguments(b);

因此，您在此处设置的参数与附加到您的 Activity 的先前参数无关。

这里是你问题的解决方案:

1. 将公共(public)方法添加到您的 Frag2 类，如下所示:

   public void passValues(float x, float y, float z){
    this.x = x;
    this.y = y;
    this.z = z;
    View view = getView();
    if(view != null){
         // set the value to views here.
    }

   }

1. 如下更改 MainActivity 中的 onSendValues 方法:

@Override
public void onSendValues(float x, float y, float z) {
    Frag2 frag2 = (Frag2)getFragmentManager().findFragmentById (R.id.frag_2);
   frag2.passValues(x, y, z);
}