我可以在 setcontentview 之前以编程方式创建 ImageView android

Question

我可以在 android 中的 setContentView(R.layout.activity_main); 之前以编程方式初始化 ImageView 或任何其他视图吗？？

实际上我得到了一个自定义实例 class（不是 activity）在全局 onCreate 方法之前像这样

MyInAppPurchaseBilling myInAppPurchaseBilling = new MyInAppPurchaseBilling(MenuClass.this);

并且在 class 构造函数中我必须使用该上下文来初始化我的偏好 class

public MyInAppPurchaseBilling(Activity launcher) {
        this.activity = launcher;
        tinyDB= new TinyDB(launcher);
    }

这是我面临的logcat错误

07-05 17:22:01.852 9660-9660/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.write.urdu.poetry.urdutexteditor, PID: 9660
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.write.urdu.poetry.urdutexteditor/com.write.urdu.poetry.urdutexteditor.MenuClass}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2339)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494)
    at android.app.ActivityThread.access0(ActivityThread.java:157)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1356)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5551)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
    at android.content.ContextWrapper.getPackageName(ContextWrapper.java:133)
    at android.preference.PreferenceManager.getDefaultSharedPreferencesName(PreferenceManager.java:375)
    at android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:370)
    at com.write.urdu.poetry.urdutexteditor.TinyDB.<init>(TinyDB.java:55)
    at com.write.urdu.poetry.urdutexteditor.inapppurchase.MyInAppPurchaseBilling.<init>(MyInAppPurchaseBilling.java:48)
    at com.write.urdu.poetry.urdutexteditor.MenuClass.<init>(MenuClass.java:38)
    at java.lang.Class.newInstance(Native Method)
    at android.app.Instrumentation.newActivity(Instrumentation.java:1068)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2329)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494) 
    at android.app.ActivityThread.access0(ActivityThread.java:157) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1356) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:148) 
    at android.app.ActivityThread.main(ActivityThread.java:5551) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)

Answer 1

你要做的是

   View view  = getLayoutInflater().inflate(R.layout.activity_main, null, false);
    imageView  = (ImageView) view.findViewById(R.id.image);

    setContentView(view);

Answer 2

试试这个：

View view = View.inflate(this, R.layout.activity_main, null); // view Exists after this code
TextView t = (TextView) view.findViewById(R.id.text);
setContentView(view);
t.setText("something");

在这里您可以看到 findViewById() 在 setContentView() 之前被调用。然而，该视图存在，因为它是膨胀的，但它可能对您有所帮助。

Answer 3

MyInAppPurchaseBilling对象是在执行MenuClass.this对象的构造函数的同时创建的吗？在这种情况下（也许直到 onCreate() 在 MenuClass.this 上被调用，但我不确定这一点）Activity 对象内的上下文（在这种情况下说 MenuClass.this ) 尚未设置。

Answer 4

这是我的 MenuClass Activity 代码，我在 setContentView() 之前在 MenuClass onCreate() 方法中初始化 TinyDB，并在从首选项 class

中获取保存的布尔值后完成我的工作

public class MenuClass extends Activity {

TinyDB tinyDB;    
    MyInAppPurchaseBilling myInAppPurchaseBilling = new MyInAppPurchaseBilling(MenuClass.this);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        myInAppPurchaseBilling.onCreate();

    tinyDB= new TinyDB(MenuClass.this);
        if (!tinyDB.getBoolean(Constant.isAdsDisabled)) {
//do your work
        }
        setContentView(R.layout.activity_menu_class);
   }
}

这是我的 MyInAppPurchaseBilling 的代码 class 我在它的构造函数中什么也没做但是创建了单独的 onCreate 方法就像 activity 的 onCreate 并在其中初始化 TinyDB 并调用了 onCreate 方法在 super.*** 行之后的 MenuClass onCreate 中的这个 class ......这样我在 MyInAppPurchaseBilling class 中成功初始化 TinyDB 以将布尔值放在应用程序的开始并在 Menuclass 之后进行进一步处理

      public class MyInAppPurchaseBilling {

            private TinyDB tinyDB;    
            Activity activity;

            public MyInAppPurchaseBilling(Activity launcher) {
                this.activity = launcher;
            }

            public void onCreate() {
                tinyDB= new TinyDB(activity);
    }
}

我可以在 setcontentview 之前以编程方式创建 ImageView android

can i create ImageView programmatically before setcontentview android

java

android

constructor

instance

android-context