Android 带有getSupportFragmentManager函数的nullPointerException
我需要你的帮助。我正在尝试从智能手机的传感器读取数据。这就是为什么我试着写一些代码。过了一会儿，我在网上找到了一个密码。但它不工作，我不知道为什么。在该代码中，有两个页面，一个用于选择传感器，另一个用于获取数据 我在这里复制代码。最后我会告诉你问题出在哪里 这是主要的活动代码Android 带有getSupportFragmentManager函数的nullPointerException,android,null,Android,Null,我需要你的帮助。我正在尝试从智能手机的传感器读取数据。这就是为什么我试着写一些代码。过了一会儿，我在网上找到了一个密码。但它不工作，我不知道为什么。在该代码中，有两个页面，一个用于选择传感器，另一个用于获取数据 我在这里复制代码。最后我会告诉你问题出在哪里 这是主要的活动代码 package com.example.sensorlistactivity; import android.os.Bundle; import android.support.v4.app.FragmentA
package com.example.sensorlistactivity;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
public class SensorListActivity extends FragmentActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.sensor_main);
SensorSelectorFragment sensorSelect = (SensorSelectorFragment) getSupportFragmentManager()
.findFragmentById(R.id.frag_sensor_select);
SensorDisplayFragment sensorDisplay = (SensorDisplayFragment) getSupportFragmentManager()
.findFragmentById(R.id.frag_sensor_view);
sensorSelect.setSensorDisplay(sensorDisplay);
}
}
package com.example.sensorlistactivity;
import java.util.List;
import android.app.Activity;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.app.ListFragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;
public class SensorSelectorFragment extends ListFragment {
private static final String TAG = "SensorSelectorFragment";
private SensorDisplayFragment sensorDisplay;
public void setSensorDisplay(SensorDisplayFragment sensorDisplay) {
this.sensorDisplay = sensorDisplay;
SensorManager sensorManager = (SensorManager) getActivity()
.getSystemService(Activity.SENSOR_SERVICE);
List<Sensor> sensors = sensorManager.getSensorList(Sensor.TYPE_ALL);
this.setListAdapter(new SensorListAdapter(getActivity()
.getApplicationContext(), android.R.layout.simple_list_item_1,
sensors));
}
private void showSensorFragment(Sensor sensor) {
sensorDisplay.displaySensor(sensor);
FragmentTransaction ft = getActivity().getSupportFragmentManager()
.beginTransaction();
ft.hide(this);
ft.show(sensorDisplay);
ft.addToBackStack("Showing sensor: " + sensor.getName());
ft.commit();
}
private class SensorListAdapter extends ArrayAdapter<Sensor> {
public SensorListAdapter(Context context, int textViewResourceId,
List<Sensor> sensors) {
super(context, textViewResourceId, sensors);
}
@Override
public View getView(final int position, View convertView,
ViewGroup parent) {
final Sensor selectedSensor = getItem(position);
if (convertView == null) {
convertView = LayoutInflater.from(getContext()).inflate(
android.R.layout.simple_list_item_1, null);
}
((TextView) convertView).setText(selectedSensor.getName());
convertView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (BuildConfig.DEBUG) {
Log.d(TAG,
"display sensor! " + selectedSensor.getName());
}
showSensorFragment(selectedSensor);
}
});
return convertView;
}
}
}
SensorSelectorFragment sensorSelect = (SensorSelectorFragment) getSupportFragmentManager()
.findFragmentById(R.id.frag_sensor_select);
SensorDisplayFragment sensorDisplay = (SensorDisplayFragment) getSupportFragmentManager()
.findFragmentById(R.id.frag_sensor_view);
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
>
<fragment
android:id="@+id/frag_sensor_select"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
class="root.gast.playground.sensor.SensorSelectorFragment" />
<fragment
android:id="@+id/frag_sensor_view"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
class="root.gast.playground.sensor.SensorDisplayFragment" />
</LinearLayout>
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fillViewport="true">
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical" >
<RadioGroup android:id="@+id/sensorRateSelector"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true" >
<RadioButton android:id="@+id/delayFastest"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="SENSOR_DELAY_FASTEST"
android:checked="false"/>
<RadioButton android:id="@+id/delayGame"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="SENSOR_DELAY_GAME"
android:checked="false"/>
<RadioButton android:id="@+id/delayNormal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="SENSOR_DELAY_NORMAL"
android:checked="true"/>
<RadioButton android:id="@+id/delayUi"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="SENSOR_DELAY_UI"
android:checked="false"/>
</RadioGroup>
<View android:id="@+id/seperator"
style="@style/line_separator"
android:layout_below="@id/sensorRateSelector" />
<TextView android:id="@+id/nameLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/seperator"
android:layout_alignParentLeft="true"
android:text="Name:"
android:layout_marginRight="5dip" />
<TextView android:id="@+id/name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/nameLabel"
android:layout_alignTop="@id/nameLabel"
android:layout_alignBottom="@id/nameLabel" />
<TextView android:id="@+id/typeLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/nameLabel"
android:layout_below="@id/nameLabel"
android:text="Type:"
android:layout_marginRight="5dip" />
<TextView android:id="@+id/type"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/typeLabel"
android:layout_alignTop="@id/typeLabel"
android:layout_alignBottom="@id/typeLabel"/>
<TextView android:id="@+id/maxRangeLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/nameLabel"
android:layout_below="@id/typeLabel"
android:text="Max Range:"
android:layout_marginRight="5dip" />
<TextView android:id="@+id/maxRange"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/maxRangeLabel"
android:layout_alignTop="@id/maxRangeLabel"
android:layout_alignBottom="@id/maxRangeLabel"/>
<TextView android:id="@+id/minDelayLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/maxRangeLabel"
android:layout_below="@id/maxRangeLabel"
android:text="Min Delay:"
android:layout_marginRight="5dip" />
<TextView android:id="@+id/minDelay"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/minDelayLabel"
android:layout_alignTop="@id/minDelayLabel"
android:layout_alignBottom="@id/minDelayLabel"/>
<TextView android:id="@+id/powerLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/minDelayLabel"
android:layout_below="@id/minDelayLabel"
android:text="Power:"
android:layout_marginRight="5dip" />
<TextView android:id="@+id/power"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/powerLabel"
android:layout_alignTop="@id/powerLabel"
android:layout_alignBottom="@id/powerLabel"
android:layout_marginRight="5dip"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/power"
android:layout_alignTop="@id/power"
android:layout_alignBottom="@id/power"
android:text="mA"/>
<TextView android:id="@+id/resolutionLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/powerLabel"
android:layout_below="@id/powerLabel"
android:text="Resolution:"
android:layout_marginRight="5dip" />
<TextView android:id="@+id/resolution"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/resolutionLabel"
android:layout_alignTop="@id/resolutionLabel"
android:layout_alignBottom="@id/resolutionLabel"/>
<TextView android:id="@+id/vendorLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/resolutionLabel"
android:layout_below="@id/resolutionLabel"
android:text="Vendor:"
android:layout_marginRight="5dip" />
<TextView android:id="@+id/vendor"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/vendorLabel"
android:layout_alignTop="@id/vendorLabel"
android:layout_alignBottom="@id/vendorLabel"/>
<TextView android:id="@+id/versionLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/versionLabel"
android:layout_alignLeft="@id/vendorLabel"
android:layout_below="@id/vendorLabel"
android:text="Version:"
android:layout_marginRight="5dip" />
<TextView android:id="@+id/version"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/versionLabel"
android:layout_alignTop="@id/versionLabel"
android:layout_alignBottom="@id/versionLabel"/>
<TextView android:id="@+id/accuracyLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/versionLabel"
android:layout_below="@id/versionLabel"
android:text="Accuracy:"
android:layout_marginRight="5dip" />
<TextView android:id="@+id/accuracy"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/accuracyLabel"
android:layout_alignTop="@id/accuracyLabel"
android:layout_alignBottom="@id/accuracyLabel"/>
<!-- timestamp -->
<TextView android:id="@+id/timestampLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/accuracyLabel"
android:layout_below="@id/accuracyLabel"
android:layout_marginRight="5dip"
android:text="Timestamp:" />
<TextView android:id="@+id/timestamp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/timestampLabel"
android:layout_alignTop="@id/timestampLabel"
android:layout_alignBottom="@id/timestampLabel"
android:layout_marginRight="5dip"
android:visibility="gone" />
<TextView android:id="@+id/timestampUnits"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/timestamp"
android:layout_alignTop="@id/timestamp"
android:layout_alignBottom="@id/timestamp"
android:visibility="gone"
android:text="(ns)" />
<TextView android:id="@+id/dataLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/accuracyLabel"
android:layout_below="@id/timestampLabel"
android:layout_marginRight="5dip"
android:visibility="gone"/>
<TextView android:id="@+id/dataUnits"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/dataLabel"
android:layout_alignTop="@id/dataLabel"
android:layout_alignBottom="@id/dataLabel"
android:visibility="gone" />
<TextView android:id="@+id/singleValue"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/dataUnits"
android:layout_alignTop="@id/dataUnits"
android:layout_alignBottom="@id/dataUnits"
android:visibility="gone" />
<!-- X axis -->
<TextView android:id="@+id/xAxisLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/dataLabel"
android:layout_below="@id/dataLabel"
android:layout_marginRight="5dip"
android:visibility="gone"
android:text="@string/xAxisLabel" />
<TextView android:id="@+id/xAxis"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/xAxisLabel"
android:layout_alignTop="@id/xAxisLabel"
android:layout_alignBottom="@id/xAxisLabel"
android:layout_marginRight="5dip"
android:visibility="gone" />
<!-- Y axis -->
<TextView android:id="@+id/yAxisLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/xAxisLabel"
android:layout_below="@id/xAxisLabel"
android:layout_marginRight="5dip"
android:visibility="gone"
android:text="@string/yAxisLabel" />
<TextView android:id="@+id/yAxis"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/yAxisLabel"
android:layout_alignTop="@id/yAxisLabel"
android:layout_alignBottom="@id/yAxisLabel"
android:layout_marginRight="5dip"
android:visibility="gone" />
<!-- Z axis -->
<TextView android:id="@+id/zAxisLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/yAxisLabel"
android:layout_below="@id/yAxisLabel"
android:layout_marginRight="5dip"
android:visibility="gone"
android:text="@string/zAxisLabel" />
<TextView android:id="@+id/zAxis"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/zAxisLabel"
android:layout_alignTop="@id/zAxisLabel"
android:layout_alignBottom="@id/zAxisLabel"
android:layout_marginRight="5dip"
android:visibility="gone" />
<!-- cos value (for rotation vector only) -->
<TextView android:id="@+id/cosLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/zAxisLabel"
android:layout_below="@id/zAxisLabel"
android:layout_marginRight="5dip"
android:visibility="gone"
android:text="cos(\u0398/2):" />
<TextView android:id="@+id/cos"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/cosLabel"
android:layout_alignTop="@id/cosLabel"
android:layout_alignBottom="@id/cosLabel"
android:layout_marginRight="5dip"
android:visibility="gone" />
</RelativeLayout>
</ScrollView>
在没有看到您的清单的情况下，我无法100%回答这个问题，但我认为现在的情况是应用程序无法构建显示，因为它无法引用您的传感器片段。以下是SensorDisplayFragment的包声明：
package com.example.sensorlistactivity;
class="com.example.sensorlistactivity.SensorDisplayFragment" />
class="com.example.sensorlistactivity.SensorDisplayFragment" />