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”。我连接了手机并再次运行，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(...)

Answer 2

我将您的代码修改为如下，并且可以正常工作（将 requestWindowFeature 放在 super.onCreate 之前：

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        super.onCreate(savedInstanceState);
        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);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

请尝试！

Answer 3

我认为这与您的图像视图无关，请尝试通过更改样式中的应用主题来更改使应用全屏显示的方式

<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">

或者直接在清单中使用这个。

android:theme="@android:style/Theme.NoTitleBar.Fullscreen"

Answer 4

记住！不要在requestFeature() 之前调用setContentView()。

这样做会导致这个异常：

 Caused by: android.util.AndroidRuntimeException: requestFeature() must be called before adding content

这将解决您的问题：

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