我是android的初学者。我创建一个新的服务,并在android mobile API Level-23中运行它。当我按下按钮启动服务时,它显示我错误。现在我创建新项目,但问题是相同的。
**FATAL EXCEPTION: java.lang.RuntimeException: Unable to instantiate service com.example.uzair.servicesapp.myIntentService: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference**
MainActivity.java
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Gravity;
import android.view.View;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private static int i =0;
private Intent ii;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ii = new Intent(this,myIntentService.class);
Toast.makeText(this, "this is custom toast", Toast.LENGTH_SHORT).show();
}
public void clickme2(View view)
{
startService(ii);
Toast.makeText(this, " Service start toast", Toast.LENGTH_SHORT).show();
}
public void clickme(View view) {
stopService(ii);
Toast.makeText(this, "Service stop toast", Toast.LENGTH_SHORT).show();
i++;
}
}
MyIntentService.java
import android.app.IntentService;
import android.content.Intent;
import android.widget.Toast;
public class myIntentService extends IntentService {
public myIntentService()
{
super("myIntentService");
Toast.makeText(this, "IntentService Constuctor toast", Toast.LENGTH_SHORT);
}
@Override
protected void onHandleIntent(Intent intent) {
Toast.makeText(this, "OnhandleIntent toast", Toast.LENGTH_SHORT);
}
@Override
public void onDestroy() {
super.onDestroy();
Toast.makeText(this, "Destroy toast", Toast.LENGTH_SHORT);
}
@Override
public void onCreate() {
super.onCreate();
}
}
的AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.uzair.servicesapp">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service android:name=".myIntentService"/>
</application>
</manifest>
activity_main.xml中
<?xml version="1.0" encoding="utf-8"?>
<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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.uzair.servicesapp.MainActivity">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!"
android:id="@+id/textView" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="clickme"
android:text="@string/click_me"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="118dp" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="New Button"
android:id="@+id/button"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true"
android:onClick="clickme2" />
</RelativeLayout>
答案 0 :(得分:0)
您正在创建和解决服务,因此您需要在Manisfest文件中为此服务创建一个intent-filter。在清单文件编辑中:
<service android:name=".myIntentService">
<intent-filter>
<action android:name="com.example.uzair.servicesapp.myIntentService" />
</intent-filter>
</service>
答案 1 :(得分:0)
删除此行:
Toast.makeText(this, "IntentService Constuctor toast", Toast.LENGTH_SHORT);
首先,您没有在任何show()
个对象上调用Toast
,因此不显示任何对象。使用Log.d()
将消息记录到LogCat。
其次,不要在构造函数中使用this
或在Service
上调用继承的方法。
如果这没有帮助,请编辑问题并发布整个Java堆栈跟踪,而不仅仅是错误消息。