如果您对Android-以编程方式为LinearLayout设置Layout_Gravity和android编程感兴趣，那么这篇文章一定是您不可错过的。我们将详细讲解Android-以编程方式为Lin
如果您对Android-以编程方式为LinearLayout设置Layout_Gravity和android 编程感兴趣，那么这篇文章一定是您不可错过的。我们将详细讲解Android-以编程方式为LinearLayout设置Layout_Gravity的各种细节，并对android 编程进行深入的分析，此外还有关于Android LayoutInflater初始化RelativeLayout和LinearLayout的问题。、android layout_gravity 和 gravity、Android LinearLayout Why Gravity Not Work、Android linearLayout 之 layout_weight 揭秘的实用技巧。
本文目录一览：- Android-以编程方式为LinearLayout设置Layout_Gravity（android 编程）
- Android LayoutInflater初始化RelativeLayout和LinearLayout的问题。
- android layout_gravity 和 gravity
- Android LinearLayout Why Gravity Not Work
- Android linearLayout 之 layout_weight 揭秘
Android-以编程方式为LinearLayout设置Layout_Gravity（android 编程）
我遇到以下问题：我实现了一个HorizontalScrollView在一个案例中包含LinearLayout和的ImageView。在这种情况下，图像约为屏幕宽度的50％。所以我想居中。不幸的是，我发现居中的唯一方式是，使用layout_gravity="center"上LinearLayout。
这是我的xml：
<HorizontalScrollView android:layout_gravity="center" android:layout_width="fill_parent" android:layout_height="wrap_content"> <LinearLayout android:orientation="horizontal" android:layout_width="wrap_content" android:layout_height="wrap_content"> <ImageView android:src="@drawable/myImg" android:layout_width="wrap_content" android:adjustViewBounds="true" android:layout_height="150dp"/> </LinearLayout> </HorizontalScrollView>但是我需要以layout_gravity编程方式进行设置。有人知道我该如何实现这一目标或以其他方式知道吗？我在Google上找到的所有内容都不适用于此帖子。
谢谢！
答案1
小编典典做这样的事情：
LayoutParams lp = new LayoutParams(); lp.gravity= Gravity.CENTER_HORIZONTAL; myImg.setLayoutParams(lp);更新： 另一种方法：
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams( LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT); params.weight = 1.0f; params.gravity = Gravity.CENTER; imageView.setLayoutParams(params);
Android LayoutInflater初始化RelativeLayout和LinearLayout的问题。
我自定义一个MyListView extends ListView, 在自定义的MyListView的构造函数里使用LayoutInflater初始化一个布局为RelativeLayout布局，然后获取这个RelativeLayout布局的宽和高时报错，使用LinearLayout就能够正常获取。
不知道这是什么情况。
MainActivity.java:
package com.fyfeng.listviewtest;
import android.app.Activity;
import android.os.Bundle;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
主配置文件activity_main.xml：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#FFD700"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<com.fyfeng.listviewtest.MyListView
android:id="@+id/listview"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
</com.fyfeng.listviewtest.MyListView>
</RelativeLayout> 自定义的MyListView extends ListView
package com.fyfeng.listviewtest;
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
public class MyListView extends ListView {
private static final String tag = MyListView.class.getSimpleName();
private int mHeaderWidth;
private int mHeaderHeight;
public MyListView(Context context) {
super(context);
this.init();
}
public MyListView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
this.init();
}
public MyListView(Context context, AttributeSet attrs) {
super(context, attrs);
this.init();
}
private void init() {
LayoutInflater lif = (LayoutInflater) this.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View header = lif.inflate(R.layout.header, null);
this.addHeaderView(header);
measureView(header);
mHeaderWidth = header.getMeasuredWidth();
mHeaderHeight = header.getMeasuredHeight();
Log.d(tag, "header width = " + mHeaderWidth + ", height = " + mHeaderHeight);
}
// 计算headView的width及height值
private void measureView(View child) {
ViewGroup.LayoutParams p = child.getLayoutParams();
if (p == null) {
p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
}
int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0, p.width);
int lpHeight = p.height;
int childHeightSpec;
if (lpHeight > 0) {
childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight, MeasureSpec.EXACTLY);
} else {
childHeightSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
}
child.measure(childWidthSpec, childHeightSpec);
}
}
private void measureView(View child) ;这个方法是直接从osc客户端源码里拷贝过来的。
ListView的headerView配置header.xml：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world"
/>
</RelativeLayout>
初始化完这个header布局后，调用measureView(View child)方法就会报空指针异常：
08-13 23:27:37.007: D/AndroidRuntime(1337): Shutting down VM
08-13 23:27:37.007: W/dalvikvm(1337): threadid=3: thread exiting with uncaught exception (group=0x4001aa28)
08-13 23:27:37.007: E/AndroidRuntime(1337): Uncaught handler: thread main exiting due to uncaught exception
08-13 23:27:37.017: E/AndroidRuntime(1337): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.fyfeng.listviewtest/com.fyfeng.listviewtest.MainActivity}: android.view.InflateException: Binary XML file line #12: Error inflating class java.lang.reflect.Constructor
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2401)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2417)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.app.ActivityThread.access$2100(ActivityThread.java:116)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.os.Handler.dispatchMessage(Handler.java:99)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.os.Looper.loop(Looper.java:123)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.app.ActivityThread.main(ActivityThread.java:4203)
08-13 23:27:37.017: E/AndroidRuntime(1337): at java.lang.reflect.Method.invokeNative(Native Method)
08-13 23:27:37.017: E/AndroidRuntime(1337): at java.lang.reflect.Method.invoke(Method.java:521)
08-13 23:27:37.017: E/AndroidRuntime(1337): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
08-13 23:27:37.017: E/AndroidRuntime(1337): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)
08-13 23:27:37.017: E/AndroidRuntime(1337): at dalvik.system.NativeStart.main(Native Method)
08-13 23:27:37.017: E/AndroidRuntime(1337): Caused by: android.view.InflateException: Binary XML file line #12: Error inflating class java.lang.reflect.Constructor
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.view.LayoutInflater.createView(LayoutInflater.java:512)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:564)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.view.LayoutInflater.rInflate(LayoutInflater.java:617)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.view.LayoutInflater.inflate(LayoutInflater.java:407)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.view.LayoutInflater.inflate(LayoutInflater.java:320)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.view.LayoutInflater.inflate(LayoutInflater.java:276)
08-13 23:27:37.017: E/AndroidRuntime(1337): at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:313)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.app.Activity.setContentView(Activity.java:1620)
08-13 23:27:37.017: E/AndroidRuntime(1337): at com.fyfeng.listviewtest.MainActivity.onCreate(MainActivity.java:20)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364)
08-13 23:27:37.017: E/AndroidRuntime(1337): ... 11 more
08-13 23:27:37.017: E/AndroidRuntime(1337): Caused by: java.lang.reflect.InvocationTargetException
08-13 23:27:37.017: E/AndroidRuntime(1337): at com.fyfeng.listviewtest.MyListView.<init>(MyListView.java:30)
08-13 23:27:37.017: E/AndroidRuntime(1337): at java.lang.reflect.Constructor.constructNative(Native Method)
08-13 23:27:37.017: E/AndroidRuntime(1337): at java.lang.reflect.Constructor.newInstance(Constructor.java:446)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.view.LayoutInflater.createView(LayoutInflater.java:499)
08-13 23:27:37.017: E/AndroidRuntime(1337): ... 21 more
08-13 23:27:37.017: E/AndroidRuntime(1337): Caused by: java.lang.NullPointerException
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:427)
08-13 23:27:37.017: E/AndroidRuntime(1337): at android.view.View.measure(View.java:7703)
08-13 23:27:37.017: E/AndroidRuntime(1337): at com.fyfeng.listviewtest.MyListView.measureView(MyListView.java:65)
08-13 23:27:37.017: E/AndroidRuntime(1337): at com.fyfeng.listviewtest.MyListView.init(MyListView.java:39)
08-13 23:27:37.017: E/AndroidRuntime(1337): ... 25 more
08-13 23:27:37.027: I/dalvikvm(1337): threadid=7: reacting to signal 3
08-13 23:27:37.027: E/dalvikvm(1337): Unable to open stack trace file ''/data/anr/traces.txt'': Permission denied
如果把header.xml中的RelativeLayout改为LinearLayout一切正常，能够获取宽和高。
谁遇到这种问题？有解的赐教一下。
android layout_gravity 和 gravity
LinearLayout 有两个非常相似的属性：
android:gravity 与 android:layout_gravity。（RelativeLayout 是没有 android:layout_gravity 属性的）
他们的区别在于：
android:gravity 属性是对该 view 中内容的限定．比如一个 button 上面的 text. 你可以设置该 text 相对于 view 的靠左，靠右等位置．(文本图片等)
android:layout_gravity 是用来设置该 view 相对与父 view 的位置．比如一个 button 在 linearlayout 里，你想把该 button 放在 linearlayout 里靠左、靠右等位置就可以通过该属性设置．
即 android:gravity 用于设置 View 中内容相对于 View 组件的对齐方式，而 android:layout_gravity 用于设置 View 组件相对于 Container 的对齐方式。
代码实现：
查看 SDK 发现有一个 setGravity 方法， 顾名思义， 这个应该就是用来设置 Button 组件中文字的对齐方式的方法了
LinearLayout 的 LayoutParams， 果然有所发现， 里面有一个 gravity 属性，相信这个就是用来设置组件相对于容器本身的位置了
Button button = new Button(this);
button.setText("One");
LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
//此处相当于布局文件中的Android:layout_gravity属性
lp.gravity = Gravity.RIGHT;
button.setLayoutParams(lp);
//此处相当于布局文件中的Android：gravity属性
button.setGravity(Gravity.CENTER);
LinearLayout linear = new LinearLayout(this);
//注意，对于LinearLayout布局来说，设置横向还是纵向是必须的！否则就看不到效果了。
linear.setOrientation(LinearLayout.VERTICAL);
linear.addView(button);
setContentView(linear);
params = new RelativeLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
params.addRule(RelativeLayout.CENTER_IN_PARENT);
mContainer.addView(progress,params);
Android LinearLayout Why Gravity Not Work
Some Android Developer may not know well of Linearlayout . This may help you to know sth about the gravity of its chilren;
-------------------CONET ------------------
1) wahts the diffrence between "gravity " android "layout_gravity"?
gravity: is sth to itself; this tell how you want its content to layout; Its see a TextView ; provided its wd is 200; and its content (text ) measured wd is 150; This Gravity setting will make its text align left ? top? center ? etc...
layout_gravity: is sth to its parent ; this tells it;s parent how it wants to be layed out; Again this TextView in its parent Linearlayout; Provided parent wd is 300, ht is 400;
2) WHY Does my layout_gravity not work?
layout_gravity is sth relevent to its parent orentation;
If its orentation is horizontal , top , btm , center_vertical will be effective;
else if is vertical : left , right ,center_horizontal is effective;
----------------------END--------------------------
THAT ALL FOR TODAY ! MY POOR UBUNTU INPUT METHOD!!!
Android linearLayout 之 layout_weight 揭秘
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:layout_gravity="center">
<TextView android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="风清扬"
android:gravity="center"
android:layout_weight="1.0"
android:background="@color/blue"/>
<TextView android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="无厓子"
android:gravity="center"
android:layout_weight="2.0"/>
<TextView android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="令狐冲"
android:gravity="center"
android:layout_weight="3.0"
android:background="@color/red"/>
</LinearLayout>
结果如下图：
关于Android-以编程方式为LinearLayout设置Layout_Gravity和android 编程的介绍现已完结，谢谢您的耐心阅读，如果想了解更多关于Android LayoutInflater初始化RelativeLayout和LinearLayout的问题。、android layout_gravity 和 gravity、Android LinearLayout Why Gravity Not Work、Android linearLayout 之 layout_weight 揭秘的相关知识，请在本站寻找。
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