如何设置＆＃34; custom＆＃34;查看选项
我试图在我的类中设置扩展LinearLayout的选项，在公共构造函数中设置(Context , AttributeSet)我将属性设置为TypedArray，说完了，我创建了一个使用方法Builder的类，并且我将该参数设置为View与该类（在公共构造函数中），如果我在Builder之前调用setContentView(..)，则可以，如果我稍后再打电话给我NullPointerException。
现在的问题是如何改变＆＃34;属性＆＃34;在设置布局为View之后到MainActivity课程？
简单的代码就像这样：
将onAreate（..）的MainActivity：
MyBuilder.set(new MyBuilder.Builder()
.setParam(...)
.setEtc(...)
.build());
setContentView(...);
MyObject obj = (MyObject) findViewById(R.id.myObject);
//MyObject.java get param from MyBuilder.java and use it for setup MyObject
//Works!
这就是我想要的：
setContentView(...);
//Do various op
MyBuilder.set(new MyBuilder.Builder()
.setParam(...)
.setEtc(...)
.build());
MyObject obj = (MyObject) findViewById(R.id.myObject);
//Params to MyObject is set after setContentView()
//With this flow I get NullPointerException in MyObject.java in reference to MyBuilder.java
简单的流程解释，因为它现在有效：
这就是我想要的：
这是logcat：
java.lang.RuntimeException: Unable to start activity ComponentInfo{it.michelelacorte.lib/it.michelelacorte.lib.MainActivity}: android.view.InflateException: Binary XML file line #56: Binary XML file line #56: Error inflating class it.michelelacorte.lib.MyObject
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2434)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494)
at android.app.ActivityThread.access$900(ActivityThread.java:157)
at android.app.ActivityThread$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:5527)
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: android.view.InflateException: Binary XML file line #56: Binary XML file line #56: Error inflating class it.michelelacorte.lib.MyObject
at android.view.LayoutInflater.inflate(LayoutInflater.java:539)
at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:256)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:109)
at it.michelelacorte.lib.MainActivity.onCreate(MainActivity.java:114)
at android.app.Activity.performCreate(Activity.java:6272)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494)
at android.app.ActivityThread.access$900(ActivityThread.java:157)
at android.app.ActivityThread$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:5527)
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: android.view.InflateException: Binary XML file line #56: Error inflating class it.michelelacorte.lib.MyObject
at android.view.LayoutInflater.createView(LayoutInflater.java:645)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:764)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:704)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:835)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:838)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798)
at android.view.LayoutInflater.inflate(LayoutInflater.java:515)
at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:256)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:109)
at it.michelelacorte.lib.MainActivity.onCreate(MainActivity.java:114)
at android.app.Activity.performCreate(Activity.java:6272)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494)
at android.app.ActivityThread.access$900(ActivityThread.java:157)
at android.app.ActivityThread$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:5527)
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.reflect.InvocationTargetException
at java.lang.reflect.Constructor.newInstance(Native Method)
at android.view.LayoutInflater.createView(LayoutInflater.java:619)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:764)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:704)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:835)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:838)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798)
at android.view.LayoutInflater.inflate(LayoutInflater.java:515)
at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:256)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:109)
at it.michelelacorte.lib.MainActivity.onCreate(MainActivity.java:114)
at android.app.Activity.performCreate(Activity.java:6272)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494)
at android.app.ActivityThread.access$900(ActivityThread.java:157)
at android.app.ActivityThread$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:5527)
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 'float it.michelelacorte.lib.MyBuilder.getRadius()' on a null object reference
at it.michelelacorte.lib.MyObject.<init>(MyObject.java:90)
at java.lang.reflect.Constructor.newInstance(Native Method)
at android.view.LayoutInflater.createView(LayoutInflater.java:619)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:764)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:704)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:835)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:838)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798)
at android.view.LayoutInflater.inflate(LayoutInflater.java:515)
at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:256)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:109)
at it.michelelacorte.lib.MainActivity.onCreate(MainActivity.java:114)
at android.app.Activity.performCreate(Activity.java:6272)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494)
at android.app.ActivityThread.access$900(ActivityThread.java:157)
at android.app.ActivityThread$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:5527)
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)
2 个答案:
答案 0 :(得分：1)
您使用setContentView()设置的XML资源包含标记<it.michelelacorte.lib.MyObject .../>。在构造函数MyObject.<init>()中，您将获得MyBuilder的实例并使用它来设置布局。
但是，由于您只在设置内容视图后初始化MyBuilder，因此您只获得null个实例，因此只有NullPointerException。
而是在MyObject
public void setup() {
MyBuilder builder = MyBuilder.get();
if (builder != null) {
// setup view with builder
} else {
// setup view defaults
}
}
处理此问题并在onCreate()
MyObject obj = (MyObject) findViewById(R.id.myObject);
obj.setup();
和构造函数本身
public MyObject() {
super(...);
setup();
}
答案 1 :(得分：0)
您可以使用LayoutInflater类createView方法执行此操作。
方法签名为createView(name, prefix, attrs)，其中attrs是AttributeSet
这里有一些关于这种方法的简短文档， more about LinearLayout
-
<强>参数：
- name要实例化的类的全名。
- attrs为此实例提供的XML属性。
- 前缀
-
退货：
- 查看新实例化的
view或null。
- 查看新实例化的
-
<强>抛出：
- ClassNotFoundException的
- InflateException
尝试以这种方式使用它
LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
inflater.createView(name, prefix, attrs);
你想在MainActivity中使用它，所以我确定定义LayoutInflater
但如果您对此有任何疑问，请对此帖发表评论，我将指导您如何操作。
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