Just beginning to learn Android development, facing a simple example of a book to write again, the results of running to use the simulator, always prompt Unfortunately, Activity has stopped., Less code, I hope to know to be able to help solve what, grateful .
First code MyView.java
package picksomething.activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
public class MyView extends View {
Paint paint;
public MyView (Context context) {
super (context);
paint.setColor (Color.WHITE);
paint.setTextSize (20);
paint.setAntiAlias (true);
}
protected void onDraw (Canvas canvas) {
super.onDraw (canvas);
canvas.drawColor (Color.GRAY);
canvas.drawRect (10, 10, 110, 110, paint);
canvas.drawText ("This interface is customized View", 60, 170, paint);
}
}
The second paragraph of the code ActivityDemo.java
package picksomething.activity;
import android.os.Bundle;
import android.app.Activity;
public class ActivityDemo extends Activity {
MyView myView = new MyView (this);
Override
protected void onCreate (Bundle savedInstanceState) {
super.onCreate (savedInstanceState);
this.setContentView (myView);
}
}
These two java files, because there is no design to layout files, they do not stick layout file it, the project name is the Activity, simulator time is always running to prompt Unfortunately, Activity has stopped.
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The above information LogCat stickers out
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& Lt; activity android: name = ". VirtualSkiInstructor" & gt; & lt; / activity & gt;
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Sorry, something these days, I'll just stick.
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Thank you give pointers, plus where to ask, is added to the file you AndroidManifest.xml
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AndroidManifest.xml is configured to increase activity
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lz is not no statement ActivityDemo
manifest file in AndroidManifest.xml
Carefully check the operation flow on the lower book mentioned
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The amount, the above methods are tried, or why not. I posted about logcat inside to error, paste what AndroidManifest.xml file, you help to see.
This is the wrong message.
03-25 13: 15: 26.109: E / Trace (937): error opening trace file: No such file or directory (2)
03-25 13: 15: 26.339: D / AndroidRuntime (937): Shutting down VM
03-25 13: 15: 26.399: W / dalvikvm (937): threadid = 1: thread exiting with uncaught exception (group = 0x40a71930)
03-25 13: 15: 26.459: E / AndroidRuntime (937): FATAL EXCEPTION: main
03-25 13: 15: 26.459: E / AndroidRuntime (937): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo {picksomething.activity / picksomething.activity.ActivityDemo}: java.lang.NullPointerException
03-25 13: 15: 26.459: E / AndroidRuntime (937): at android.app.ActivityThread.performLaunchActivity (ActivityThread.java:2106)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at android.app.ActivityThread.handleLaunchActivity (ActivityThread.java:2230)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at android.app.ActivityThread.access $ 600 (ActivityThread.java:141)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at android.app.ActivityThread $ H.handleMessage (ActivityThread.java:1234)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at android.os.Handler.dispatchMessage (Handler.java:99)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at android.os.Looper.loop (Looper.java:137)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at android.app.ActivityThread.main (ActivityThread.java:5041)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at java.lang.reflect.Method.invokeNative (Native Method)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at java.lang.reflect.Method.invoke (Method.java:511)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run (ZygoteInit.java:793)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:560)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at dalvik.system.NativeStart.main (Native Method)
03-25 13: 15: 26.459: E / AndroidRuntime (937): Caused by: java.lang.NullPointerException
03-25 13: 15: 26.459: E / AndroidRuntime (937): at android.content.ContextWrapper.getResources (ContextWrapper.java:89)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at android.view.ContextThemeWrapper.getResources (ContextThemeWrapper.java:78)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at android.view.View & lt; init & gt; (View.java:3226)
.03-25 13: 15: 26.459: E / AndroidRuntime (937): at picksomething.activity.MyView & lt; init & gt; (MyView.java:11)
.03-25 13: 15: 26.459: E / AndroidRuntime (937): at picksomething.activity.ActivityDemo & lt; init & gt; (ActivityDemo.java:9)
.03-25 13: 15: 26.459: E / AndroidRuntime (937): at java.lang.Class.newInstanceImpl (Native Method)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at java.lang.Class.newInstance (Class.java:1319)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at android.app.Instrumentation.newActivity (Instrumentation.java:1054)
03-25 13: 15: 26.459: E / AndroidRuntime (937): at android.app.ActivityThread.performLaunchActivity (ActivityThread.java:2097)
03-25 13: 15: 26.459: E / AndroidRuntime (937): ... 11 more
03-25 13: 15: 30.619: I / Process (937): Sending signal PID:. 937 SIG: 9
This is AndroidManifest.xml file.
& Lt;? Xml version = "1.0" encoding = "utf-8" & gt;?
& Lt; manifest xmlns: android = "http://schemas.android.com/apk/res/android"
package = "picksomething.activity"
android: versionCode = "1"
android: versionName = "1.0" & gt;
& Lt; uses-sdk
android: minSdkVersion = "8"
android: targetSdkVersion = "17" / & gt;
& Lt; application
android: allowBackup = "true"
android: icon = "@ drawable / ic_launcher"
android: label = "@ string / app_name"
android: theme = "@ style / AppTheme" & gt;
& Lt; activity
android: name = "picksomething.activity.ActivityDemo"
android: label = "@ string / app_name" & gt;
& Lt; intent-filter & gt;
& Lt; action android: name = "android.intent.action.MAIN" / & gt;
& Lt; category android: name = "android.intent.category.LAUNCHER" / & gt;
& Lt; / intent-filter & gt;
& Lt; / activity & gt;
& Lt; / application & gt;
& Lt; / manifest & gt;
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The list of documents & lt; activity android: name = "picksomething.activity.ActivityDemo"
Need to change & lt; activity android: name = "ActivityDemo"
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And the MyView (Context context) in the super (context); removal
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Amount, or not.
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Remove this sentence prompts error
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You do not have new paint it yet
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I tried it, too.
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The super (context); put the last line of the method and the paint initialization about ~
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The
MyView myView = new MyView (this);
Override
protected void onCreate (Bundle savedInstanceState) {
super.onCreate (savedInstanceState);
this.setContentView (myView);
}
Read:
Override
protected void onCreate (Bundle savedInstanceState) {
super.onCreate (savedInstanceState);
MyView myView = new MyView (this);
this.setContentView (myView);
}
Ok, now I do not know why, I just started to learn android!
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Analysis of what know the source due to the: onCreate () function before the constructor call activity objects have run, and this time the object has not been created, so myView point to null, is not referenced, so references to him before initialization, also It is again this.setContentView (myView); before!
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Thank you! ! ! I thought for a long time or did not result, the last against your approach to solve the
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I am also a beginner, experienced similar problems. Tinkering in AndroidManifest.xml file
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What is the specific solution is? I am also a beginner
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I also encountered a say in AndroidMenifest.xml, but do not know how to change
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Permissions SEND_SMS
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pro, I declare again show how still ah
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I am a novice, also encountered, it has been resolved, to those who need reference
Paint paint = new Paint ();
Thank http://www.th7.cn/Program/Android/201407/246852.shtml
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