在 Android Java 中重用带有字符串参数的 onclick 监听器

Question

我正在模仿这个thread 中的代码来创建一个可重用的点击事件来启动浏览器。我想在实例化类时传递一个自定义 URL 目标。该示例在 eclipse 中没有明显错误，但在启动时崩溃：

FATAL EXCEPTION: main 02-19 12:45:57.416: E/AndroidRuntime(12465): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.app/com.app.ItemActivity}: java.lang.NullPointerException

错误应该来自这一行 btn.setOnClickListener(new ButtonInternetAccess("http://google.com"));

因为没有那条线它可以正常工作。 ButtonInternetAccess 类是否无法返回导致 null 值的 onClickListener？我该如何解决？

主要活动：

public class ItemActivity extends ActionBarActivity{
    private static final View View = null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_item);
        Bundle b = i.getExtras();
        Button btn = (Button) findViewById(R.id.button_internet_access);
        btn.setOnClickListener(new ButtonInternetAccess("http://google.com"));      
    }
}

按钮类：

public class ButtonInternetAccess extends Activity implements OnClickListener {
    String url;
    public ButtonInternetAccess(String url) {
        this.url = url;
    }

    public void onClick(View v) {
        try {
            Intent callIntent = new Intent(Intent.ACTION_CALL);
            callIntent.setData(Uri.parse(url));
            startActivity(callIntent); // No Error here

            System.out.println(url);
        } catch (ActivityNotFoundException activityException) {
            Log.e("Calling a Phone Number", "Call failed", activityException);
        }
    }

}

布局/activity_item

<TextView
    android:id="@+id/response"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="" />

<include android:id="@+id/header" layout="@layout/button_internet_access">

布局/button_internet_access：

<Button xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/button_internet_access"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="go out" />

错误：

02-19 12:45:57.416: E/AndroidRuntime(12465): FATAL EXCEPTION: main
02-19 12:45:57.416: E/AndroidRuntime(12465): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.app/com.app.ItemActivity}: java.lang.NullPointerException
02-19 12:45:57.416: E/AndroidRuntime(12465):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at android.app.ActivityThread.access$600(ActivityThread.java:130)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at android.os.Handler.dispatchMessage(Handler.java:99)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at android.os.Looper.loop(Looper.java:137)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at android.app.ActivityThread.main(ActivityThread.java:4745)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at java.lang.reflect.Method.invokeNative(Native Method)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at java.lang.reflect.Method.invoke(Method.java:511)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at dalvik.system.NativeStart.main(Native Method)
02-19 12:45:57.416: E/AndroidRuntime(12465): Caused by: java.lang.NullPointerException
02-19 12:45:57.416: E/AndroidRuntime(12465):    at com.app.ItemActivity.onCreate(ItemActivity.java:29)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at android.app.Activity.performCreate(Activity.java:5008)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
02-19 12:45:57.416: E/AndroidRuntime(12465):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)

更新：

我已经设法在这个link之后制作了一个插件。

最后的工作：

类互联网：

public class Internet implements OnClickListener {

    private String url;
    private Context context;

    public Internet(Context context, String url) {
        this.context = context;
        this.url = url;
    }

    @Override
    public void onClick(View v) {

        if (!url.contains("http://")){
            url = "http://"+url;
        }
        Intent callIntent = new Intent(Intent.ACTION_VIEW);
        callIntent.setData(Uri.parse(url));
        context.startActivity(callIntent);
    }
}

类样式按钮：

public class StyleButton extends Button{

    public StyleButton(Context context) {
        super(context);
    }

    public StyleButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        initStyleButton(attrs);
    }

    public StyleButton(Context context, AttributeSet attrs, int defStyle,String url) {
        super(context, attrs, defStyle);
        initStyleButton(attrs);
    }

    private void initStyleButton(AttributeSet attrs){
        TypedArray a = getContext().obtainStyledAttributes(attrs,R.styleable.style_Button);
        String Text1 = a.getString(R.styleable.style_Button_myText_1);
        String Text2 = a.getString(R.styleable.style_Button_myText_2);
        setText(Text1 + "\n" + Text2);
        String url = a.getString(R.styleable.style_Button_url);
        System.out.println(url);
        setOnClickListener(new Internet(getContext(),url));
        a.recycle();
    }
}

/layout/item_activity

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:stylebutton= "http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:id="@+id/response"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text=""/>
<com.button.StyleButton
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    stylebutton:myText_1="My Text 1"
    stylebutton:myText_2="My Text 2"
    stylebutton:url="www.google.com"
    />
<com.button.StyleButton
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    stylebutton:myText_1="Hello!"
    stylebutton:myText_2="It's a Style Button:)"
    stylebutton:url="www.yahoo.com"
    />

/value/attr.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="style_Button">
        <attr name="myText_1" format="string" />
        <attr name="myText_2" format="string" />
        <attr name="url" format="string" />
    </declare-styleable>
</resources>

Answer 1

创建您的custom button 并在您的项目中使用它，这样就可以在全球范围内使用它。

    public class ButtonInternetAccess extends UIButton implements OnClickListener {
        String url;
    Context mContext;
    public ButtonInternetAccess(Context context, AttributeSet attrs,String url) {
            super(context, attrs);
         this.url = url;
        this.mContext=mContext;
            // TODO Auto-generated constructor stub
        }
        // initialize button and add click listener here.

}

您也可以将该按钮添加到您的 xml 中

<yourpackagename.ButtonInternetAccess 
height=""
width = ""
other properties to include
/>

希望这会有所帮助。

Answer 2

您的 setOnClickListener 应如下方式：

btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                try {
                    Intent callIntent = new Intent(Intent.ACTION_CALL);
                    callIntent.setData(Uri.parse("http://google.com"));
                    startActivity(callIntent); // No Error here
                    System.out.println(url);
                } catch (ActivityNotFoundException activityException) {
                    Log.e("Calling a Phone Number", "Call failed", activityException);
                }
            }
        });

您似乎不需要将 URL 发送到另一个类，因为您可以对 ItemActivity 本身执行相同的操作。

已编辑：如果您想公开一堂课，请将您的 ButtonInternetAccess 更新为以下方式：

public class ButtonInternetAccess implements OnClickListener {
    String url;
    Context mContext;
    public ButtonInternetAccess(Context mContext,String url) {
        this.url = url;
        this.mContext=mContext;
    } 

    public void onClick(View v) {
        try { 
            Intent callIntent = new Intent(Intent.ACTION_CALL);
            callIntent.setData(Uri.parse(url));
            mContext.startActivity(callIntent);

            System.out.println(url);
        } catch (ActivityNotFoundException activityException) {
            Log.e("Calling a Phone Number", "Call failed", activityException);
        } 
    } 

} 

Answer 3

将按钮类更改为;

public class ButtonInternetAccess implements View.OnClickListener {

    private String url;
    private Context context;

    public ButtonInternetAccess(Context context, String url) {
        this.context = context;
        this.url = url;
    }

    public void onClick(View v) {

        System.out.println(url);

        Intent callIntent = new Intent(Intent.ACTION_VIEW);
        callIntent.setData(Uri.parse(url));

        try {
            context.startActivity(callIntent);
        } catch (ActivityNotFoundException activityException) {
            Log.e("ONCLICK", "No Activity found", activityException);
        }
    }
}