Question

03-23 01:06:33.111 11547-11547/com.compscitutorials.basigarcia.navigationdrawervideotutorial E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.compscitutorials.basigarcia.navigationdrawervideotutorial, PID: 11547
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
   at android.content.ComponentName.<init>(ComponentName.java:128)
   at android.content.Intent.<init>(Intent.java:4449)
   at com.forever.technology.bscit.Sem1Fragment_list.onListItemClick(Sem1Fragment_list.java:50)
   at android.support.v4.app.ListFragment$2.onItemClick(ListFragment.java:58)
   at android.widget.AdapterView.performItemClick(AdapterView.java:310)
   at android.widget.AbsListView.performItemClick(AbsListView.java:1145)
   at android.widget.AbsListView$PerformClick.run(AbsListView.java:3066)
   at android.widget.AbsListView$3.run(AbsListView.java:3903)
   at android.os.Handler.handleCallback(Handler.java:739)
   at android.os.Handler.dispatchMessage(Handler.java:95)
   at android.os.Looper.loop(Looper.java:148)
   at android.app.ActivityThread.main(ActivityThread.java:5417)
   at java.lang.reflect.Method.invoke(Native Method)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

然后我需要以编程方式设置保证金：

<RelativeLayout>

    ...

    <ImageView
      android:id="@+id/imageView1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignParentLeft="true"
      android:layout_marginLeft="10dp"
      android:layout_marginTop=”11dp”
      android:background=”@drawable/image”  />

</RelativeLayout>

ImageView仍然有marginLeft 10和marginTop 11;

有什么问题？

Answer 1

尝试使用ViewGroup.MarginLayoutParams为ImageView设置边距。以下是来自@Hiren Patel answer的方法，对我来说非常适用。

private void setMargins (View view, int left, int top, int right, int bottom) {
    if (view.getLayoutParams() instanceof ViewGroup.MarginLayoutParams) {
        ViewGroup.MarginLayoutParams p = (ViewGroup.MarginLayoutParams) view.getLayoutParams();
        p.setMargins(left, top, right, bottom);
        view.requestLayout();
    }
}

代码中如何使用的示例：

public void testMargin(View view){
    ImageView imageView = (ImageView) findViewById(R.id.imageView1);
    RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams)   imageView.getLayoutParams();
    params.width = 100;
    params.height = 100;
    setMargins(imageView , 0, 0, 0, 0);
    imageView.setLayoutParams(params);
}

我的测试布局：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/holo_blue_light"
    tools:context="com.g2o.test.TestActivity">

    <View
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_alignParentLeft="true"
        android:background="@android:color/holo_red_dark" />

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_marginLeft="100dp"
        android:layout_marginTop="100dp"
        android:adjustViewBounds="true"
        android:background="@drawable/cast_ic_notification_0" />

    <Button
        android:id="@+id/test"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:onClick="testMargin"
        android:text="Test" />" />

</RelativeLayout>

希望这会有所帮助!!

Answer 2

您是否尝试制作新的LayoutParams？

ImageView imageView = (ImageView) findViewRoot(R.id.imageView1);
RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(
    RelativeLayout.LayoutParams.WRAP_CONTENT,      
    RelativeLayout.LayoutParams.WRAP_CONTENT
);
params.setMargins(0,0,0,0);
imageView.setLayoutParams(params);

Answer 3

希望此帮助将您的ImageView放在RelativeLayout中，并将其宽度和高度设置为Match-Parent

 <RelativeLayout
                android:id="@+id/lay_expandable"
                android:layout_width="match_parent"
                android:layout_height="200dp"
                >

                <ImageView
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:src="@mipmap/ic_expansion" />

            </RelativeLayout>

，并且在您的活动中使用LinearLayout.LayoutParams 例如

LinearLayout.LayoutParams params = new LinearLayout.LayoutParams
                    (LinearLayout.LayoutParams.MATCH_PARENT, 400);
            lay_layout.setLayoutParams(params);

//请注意展开相对布局，而不是图像本身

Answer 4

这对某人可能有用：在我的情况下，我正在处理相同的问题，即在android api 19上无法识别页边距，所以我要做的是更改图像的大小（稍微增加一点），然后调整填充，如下所示：

file: dimens.xml
<dimen name="image_padding_right">5dp</dimen>

然后输入代码：

 val imageView1 = ImageView(this.activity)
 imageView1.setPadding(0,0,
 resources.getDimension(R.dimen.image_padding_right).roundToInt(), 0)
 imageView1.cropToPadding = true

使用 cropToPadding 选项可以解决此问题，以防页边空白不起作用。

希望对您有帮助。

Android setMargins无法以编程方式运行

4 个答案: