Question

我正在使用链接http://thinkandroid.wordpress.com/2010/01/24/handling-screen-off-and-screen-on-intents/中的教程，并尝试在Android手机中启用和关闭屏幕数据。但是我提出了The method onpause is undefined for the type object，OnResume方法中发生了同样的错误。我将android级别设置为10-17。

以下是整个代码：

package com.example.myfirstapp;

import android.content.BroadcastReceiver;
import android.content.Intent;
import android.content.IntentFilter;

public class ExampleActivity {
    protected void onCreate() {
        // INITIALIZE RECEIVER
        IntentFilter filter = new IntentFilter(Intent.ACTION_SCREEN_ON);
        filter.addAction(Intent.ACTION_SCREEN_OFF);
        ScreenReceiver mReceiver = new ScreenReceiver();
        registerReceiver(mReceiver, filter);
        // YOUR CODE
    }

    private void registerReceiver(ScreenReceiver mReceiver, IntentFilter filter) {
        // TODO Auto-generated method stub

    }

    protected void onPause() {
        // WHEN THE SCREEN IS ABOUT TO TURN OFF
        if (ScreenReceiver.wasScreenOn) {
            // THIS IS THE CASE WHEN ONPAUSE() IS CALLED BY THE SYSTEM DUE TO A SCREEN STATE CHANGE
            System.out.println("SCREEN TURNED OFF");
        } else {
            // THIS IS WHEN ONPAUSE() IS CALLED WHEN THE SCREEN STATE HAS NOT CHANGED
        }
        super.onPause();
    }

    protected void onResume() {
        // ONLY WHEN SCREEN TURNS ON
        if (!ScreenReceiver.wasScreenOn) {
            // THIS IS WHEN ONRESUME() IS CALLED DUE TO A SCREEN STATE CHANGE
            System.out.println("SCREEN TURNED ON");
        } else {
            // THIS IS WHEN ONRESUME() IS CALLED WHEN THE SCREEN STATE HAS NOT CHANGED
        }
        super.onResume();
    }
}

Answer 1

首先，

public class ExampleActivity {
...

对于您在Android中定义的任何活动，您必须从Activity类

进行扩展

public class ExampleActivity extends Activity {

OnCreate，OnResume和OnPause是覆盖方法，因此相应地更改它们

@Override
protected void onCreate() {
...

@Override
protected void onPause() {
...

@Override
protected void onResume() {
...

Answer 2

问题是你必须扩展Activity（检查文章以确认这一点），你还必须覆盖每个继承的方法（使用@Override表示法）。

此外，您必须删除“registerReciever”，因为此调用是从Activity继承的（并由其处理）。

我发布了我认为正确编码的内容。

package com.example.myfirstapp;

import android.content.BroadcastReceiver;
import android.content.Intent;
import android.content.IntentFilter;

public class ExampleActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // INITIALIZE RECEIVER
    IntentFilter filter = new IntentFilter(Intent.ACTION_SCREEN_ON);
    filter.addAction(Intent.ACTION_SCREEN_OFF);
    ScreenReceiver mReceiver = new ScreenReceiver();
    registerReceiver(mReceiver, filter);
    // YOUR CODE
}


@Override
protected void onPause() {
    // WHEN THE SCREEN IS ABOUT TO TURN OFF
    if (ScreenReceiver.wasScreenOn) {
        // THIS IS THE CASE WHEN ONPAUSE() IS CALLED BY THE SYSTEM DUE TO A SCREEN STATE CHANGE
        System.out.println("SCREEN TURNED OFF");
    } else {
        // THIS IS WHEN ONPAUSE() IS CALLED WHEN THE SCREEN STATE HAS NOT CHANGED
    }
    super.onPause();
}

@Override
protected void onResume() {
    // ONLY WHEN SCREEN TURNS ON
    if (!ScreenReceiver.wasScreenOn) {
        // THIS IS WHEN ONRESUME() IS CALLED DUE TO A SCREEN STATE CHANGE
        System.out.println("SCREEN TURNED ON");
    } else {
        // THIS IS WHEN ONRESUME() IS CALLED WHEN THE SCREEN STATE HAS NOT CHANGED
    }
    super.onResume();
}
}

方法未定义类型对象

2 个答案: