Question

请我还在学习java / android app开发，我的代码中有这些错误。请帮忙。

我的代码看起来像这样

package com.creditswitch;

import android.app.Activity;
import android.content.BroadcastReceiver;
import java.io.PrintStream;
import android.content.IntentFilter;

public class MainActivity extends Activity {
    BroadcastReceiver mReceiver;

      protected void onResume() {
        MyApplication.activitycontext = this;
        System.out.println("On Resume of base activity");
        if(mReceiver == null) {
            mReceiver = new ConnectionChangeReceiver();
            registerReceiver(mReceiver, localString1); //THIS LINE IS GIVING ERROR: localString1 cannot be resolved to a variable
            System.out.println("Register Receiver");
        }
        super.onResume();
    }

    protected void onPause() {
        System.out.println("On Pause of base activity");
        if(mReceiver != null) {
            unregisterReceiver(mReceiver);
            System.out.println("Unregister Receiver");
            mReceiver = 0x0; // THIS LINE IS GIVING ERROR: Type mismatch: cannot convert from int to BroadcastReceiver
        }
        super.onPause();
    }
}

Answer 1

首先应该声明localString1类型为intentFilter，因为registerReceiver方法接受两个参数： 1 BraodcastReceiver 2 IntentFilter实例您可以创建一个intent过滤器，如下所示：

 static final String MY_ACTION = "com.my.defined.MY_ACTION";
    IntentFilter intentFilter = new IntentFilter(MY_ACTION);

您必须在androidmanifest.xml的标记中提供相同的操作，这可以如此处所示完成。

 <receiver android:name="MyReceiver" >
    <intent-filter>
    <action android:name="com.my.defined.MY_ACTION" />
    </intent-filter>
    </receiver>

第二件事是你没有正确初始化mReceiver对象。它的类型为broadcastReceiver，你不能用整数值实例化它

要初始化它，你必须执行以下操作（或在类型BroadcastReceiver上创建一个匿名内部类）：

创建一个扩展BroadcastReceiver并覆盖其onreceive方法的类

公共类MyBroadcast扩展了BroadcastReceiver {
```
@Override
public void onReceive(Context context, Intent intent) {

// your code here

}
```

现在创建此类的对象，而不是在

  MyBroadcast mReceiver = new MyBroadcast();

更喜欢在你活动的oncreate方法中这样做。

现在您可以调用注册接收方法，如下所示：

registerReceiver(mReceiver,intentFilter);

Answer 2

错误1

localString1 needs to be defined and initialized

错误2

0x0 is a hexadecimal value, thus cant be a assigned to a variable of type BroadcastReceiver

Answer 3

您应该替换此代码：

registerReceiver(mReceiver, localString1);

用这个：

static final String SOME_ACTION = "com.yourcompany.yourapp.SOME_ACTION";
IntentFilter filter = new IntentFilter(SOME_ACTION);
registerReceiver(mReceiver, filter);

至于第二个错误你想做什么？如果你想将mReceiver设置为null，只需给出：

mReceiver = null;

“localString1”无法解析为变量和类型不匹配错误

3 个答案: