Android 以编程方式添加 ImageView
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原文地址: http://stackoverflow.com/questions/23135563/
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Android programmatically add ImageView
提问by Atomix
I just started learning Android programming. I created a new project (API 19) with a blank activity and tried to add an ImageView like this: (in the MainActivity's onCreate() )
我刚开始学习Android编程。我创建了一个带有空白活动的新项目（API 19），并尝试添加这样的 ImageView：（在 MainActivity 的 onCreate() 中）
setContentView(R.layout.activity_main);
View view = (View) findViewById(R.layout.activity_main);
LinearLayout picLL = new LinearLayout(MainActivity.this);
picLL.layout(0, 0, 100, 100);
picLL.setLayoutParams(new LayoutParams(100, 100));
picLL.setOrientation(LinearLayout.HORIZONTAL);
((ViewGroup) view).addView(picLL); // <- This is line 36
ImageView myImage = new ImageView(this);
myImage.setImageResource(R.drawable.ic_launcher);
picLL.addView(myImage);
However the app crashes immediately after launch. I've tried numerous other answers from Stackoverflow, but none worked. There seems to be something I am missing...
但是，该应用程序在启动后立即崩溃。我已经尝试了 Stackoverflow 的许多其他答案，但都没有奏效。似乎有什么我错过了......
This is the LogCat output:
这是 LogCat 输出：
04-17 10:02:35.611: E/AndroidRuntime(1402): FATAL EXCEPTION: main
04-17 10:02:35.611: E/AndroidRuntime(1402): Process: com.example.test, PID: 1402
04-17 10:02:35.611: E/AndroidRuntime(1402): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.test/com.example.test.MainActivity}: java.lang.NullPointerException
04-17 10:02:35.611: E/AndroidRuntime(1402): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
04-17 10:02:35.611: E/AndroidRuntime(1402): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
04-17 10:02:35.611: E/AndroidRuntime(1402): at android.app.ActivityThread.access0(ActivityThread.java:135)
04-17 10:02:35.611: E/AndroidRuntime(1402): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
04-17 10:02:35.611: E/AndroidRuntime(1402): at android.os.Handler.dispatchMessage(Handler.java:102)
04-17 10:02:35.611: E/AndroidRuntime(1402): at android.os.Looper.loop(Looper.java:136)
04-17 10:02:35.611: E/AndroidRuntime(1402): at android.app.ActivityThread.main(ActivityThread.java:5017)
04-17 10:02:35.611: E/AndroidRuntime(1402): at java.lang.reflect.Method.invokeNative(Native Method)
04-17 10:02:35.611: E/AndroidRuntime(1402): at java.lang.reflect.Method.invoke(Method.java:515)
04-17 10:02:35.611: E/AndroidRuntime(1402): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-17 10:02:35.611: E/AndroidRuntime(1402): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-17 10:02:35.611: E/AndroidRuntime(1402): at dalvik.system.NativeStart.main(Native Method)
04-17 10:02:35.611: E/AndroidRuntime(1402): Caused by: java.lang.NullPointerException
04-17 10:02:35.611: E/AndroidRuntime(1402): at com.example.test.MainActivity.onCreate(MainActivity.java:36)
04-17 10:02:35.611: E/AndroidRuntime(1402): at android.app.Activity.performCreate(Activity.java:5231)
04-17 10:02:35.611: E/AndroidRuntime(1402): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
04-17 10:02:35.611: E/AndroidRuntime(1402): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
04-17 10:02:35.611: E/AndroidRuntime(1402): ... 11 more
04-17 10:02:38.771: I/Process(1402): Sending signal. PID: 1402 SIG: 9
回答by olegr
It happens because you are trying to find Viewby layout's id.
发生这种情况是因为您试图View通过布局的 id进行查找。
View view = (View) findViewById(R.layout.activity_main);
You have two options:
You can add any id for root element in activity_main.xml. For example it will be root_layout_id. Then you can find it like:
您有两个选择：您可以在activity_main.xml. 例如，它将是root_layout_id. 然后你可以找到它：
View view = (View) findViewById(R.id.root_layout_id);
The second option is to create layout programatically at all. Change your onCreate() method like this:
第二种选择是完全以编程方式创建布局。像这样改变你的 onCreate() 方法：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
LinearLayout picLL = new LinearLayout(this);
picLL.layout(0, 0, 100, 100);
picLL.setLayoutParams(new LayoutParams(100, 100));
picLL.setOrientation(LinearLayout.HORIZONTAL);
ImageView myImage = new ImageView(this);
myImage.setImageResource(R.drawable.ic_launcher);
picLL.addView(myImage);
setContentView(picLL);
}
