java - ImageView 在 Android 中不起作用

Question

我在这段代码中创建了一个ImageView。

activity_main.xml

<ImageView
    android:id="@+id/start_windows"
    android:src="@drawable/start_windows"
    android:scaleType = "centerCrop"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:visibility="visible"
    android:layout_margin="0px"
    android:layout_marginBottom="0px"
    android:layout_marginLeft="0px"
    android:layout_marginRight="0px"
    android:layout_marginStart="0px"
    android:layout_marginTop="0px" />

MainActivity.java

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Point;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Display;
import android.view.Window;
import android.view.WindowManager;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); 
        setContentView(R.layout.activity_main);

        Display display = getWindowManager().getDefaultDisplay();
        Point size = new Point();
        display.getSize(size);
        Bitmap bmp = Bitmap.createScaledBitmap(BitmapFactory.decodeResource(getResources(), R.drawable.start_windows), size.x, size.y, true);


        ImageView iv_background = (ImageView) findViewById(R.id.start_windows);
        iv_background.setImageBitmap(bmp);
    }
}

我在模拟器中运行我的应用程序并收到错误“不幸的是，应用程序已停止”。我连接手机并再次运行，但我也遇到了同样的错误“不幸的是，应用程序已停止”。我该如何解决这个问题？

这是我在 LogCat 中显示的消息:

   08-19 23:55:22.011    2032-2032/com.newapplication E/AndroidRuntime﹕ FATAL EXCEPTION: main
        Process: com.newapplication, PID: 2032
        java.lang.RuntimeException: Unable to start activity ComponentInfo{com.newapplicationp/com.newapplication.MainActivity}: android.util.AndroidRuntimeException: requestFeature() must be called before adding content
                at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
                at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
                at android.app.ActivityThread.access$800(ActivityThread.java:151)
                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
                at android.os.Handler.dispatchMessage(Handler.java:102)
                at android.os.Looper.loop(Looper.java:135)
                at android.app.ActivityThread.main(ActivityThread.java:5257)
                at java.lang.reflect.Method.invoke(Native Method)
                at java.lang.reflect.Method.invoke(Method.java:372)
                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
         Caused by: android.util.AndroidRuntimeException: requestFeature() must be called before adding content
                at com.android.internal.policy.impl.PhoneWindow.requestFeature(PhoneWindow.java:302)
                at android.app.Activity.requestWindowFeature(Activity.java:3605)
                at com.newapplication.MainActivity.onCreate(MainActivity.java:19)
                at android.app.Activity.performCreate(Activity.java:5990)
                at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
                at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
                at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
                at android.app.ActivityThread.access$800(ActivityThread.java:151)
                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
                at android.os.Handler.dispatchMessage(Handler.java:102)
                at android.os.Looper.loop(Looper.java:135)
                at android.app.ActivityThread.main(ActivityThread.java:5257)
                at java.lang.reflect.Method.invoke(Native Method)
                at java.lang.reflect.Method.invoke(Method.java:372)
                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

Answer 1

对于AppCompat库，应在super.onCreate()之前调用requestFeature(...)