java无法启动活动组件信息NullpointerException
我想制作一个可以制作图片并保存它们的应用程序,但当我测试它时,在我的日志中出现了这样一个错误:“java.lang.RuntimeException:无法启动活动组件信息{com.example.random/com.example.random.FotoMaker}:java.lang.NullPointerException”。我认为问题与目的有关,但我不确定我需要在我的FotoMaker中添加/更改什么。爪哇
菜单屏幕。爪哇:
package com.example.random;
import 安卓.app.Activity;
import 安卓.content.Intent;
import 安卓.os.Bundle;
import 安卓.util.Log;
import 安卓.view.View;
import 安卓.view.View.OnClickListener;
import 安卓.view.Window;
import 安卓.widget.Button;
public class MenuScreen extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
findViewById(R.id.test).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Log.d("DEBUG", "test");
Intent intent = new Intent(MenuScreen.this, FotoMaker.class);
startActivityForResult(intent, 0);
}
});
findViewById(R.test1).setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Log.d("DEBUG", "test1");
Intent intent = new Intent(MenuScreen.this, FotoMaker.class);
}
});
findViewById(R.test2).setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Log.d("DEBUG", "test2");
Intent intent = new Intent(MenuScreen.this, FotoMaker.class);
}
});
findViewById(R.id.verlaat_app).setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Log.d("DEBUG", "test3");
MenuScreen.this.finish();
}
});
}
}
菜单屏幕。爪哇:
package com.example.random;
import 安卓.app.Activity;
import 安卓.content.Intent;
import 安卓.graphics.Bitmap;
import 安卓.os.Bundle;
import 安卓.view.View;
import 安卓.view.View.OnClickListener;
import 安卓.widget.Button;
import 安卓.widget.ImageView;
public class FotoMaker extends Activity
{
ImageView iv;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.testpic);
iv = (ImageView) findViewById(R.id.imageView);
Button btn = (Button) findViewById(R.id.testpic);
btn.setOnClickListener(new OnClickListener()
{
@Override
public void onClick (View v){
Intent intent = new Intent(安卓.provider.MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(intent, 0);
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
if(requestCode == 0)
{
Bitmap theImage = (Bitmap) data.getExtras().get("data");
iv.setImageBitmap(theImage);
}
}
}
LogCat:
11-16 18:30:14.366: E/AndroidRuntime(1522): FATAL EXCEPTION: main
11-16 18:30:14.366: E/AndroidRuntime(1522): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.random/com.example.random.FotoMaker}: java.lang.NullPointerException
11-16 18:30:14.366: E/AndroidRuntime(1522): at 安卓.app.ActivityThread.performLaunchActivity(ActivityThread.java:1996)
11-16 18:30:14.366: E/AndroidRuntime(1522): at 安卓.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2023)
11-16 18:30:14.366: E/AndroidRuntime(1522): at 安卓.app.ActivityThread.access$600(ActivityThread.java:127)
11-16 18:30:14.366: E/AndroidRuntime(1522): at 安卓.app.ActivityThread$H.handleMessage(ActivityThread.java:1174)
11-16 18:30:14.366: E/AndroidRuntime(1522): at 安卓.os.Handler.dispatchMessage(Handler.java:99)
11-16 18:30:14.366: E/AndroidRuntime(1522): at 安卓.os.Looper.loop(Looper.java:137)
11-16 18:30:14.366: E/AndroidRuntime(1522): at 安卓.app.ActivityThread.main(ActivityThread.java:4503)
11-16 18:30:14.366: E/AndroidRuntime(1522): at java.lang.reflect.Method.invokeNative(Native Method)
11-16 18:30:14.366: E/AndroidRuntime(1522): at java.lang.reflect.Method.invoke(Method.java:511)
11-16 18:30:14.366: E/AndroidRuntime(1522): at com.安卓.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:809)
11-16 18:30:14.366: E/AndroidRuntime(1522): at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:576)
11-16 18:30:14.366: E/AndroidRuntime(1522): at dalvik.system.NativeStart.main(Native Method)
11-16 18:30:14.366: E/AndroidRuntime(1522): Caused by: java.lang.NullPointerException
11-16 18:30:14.366: E/AndroidRuntime(1522): at com.example.random.FotoMaker.onCreate(FotoMaker.java:27)
11-16 18:30:14.366: E/AndroidRuntime(1522): at 安卓.app.Activity.performCreate(Activity.java:4479)
11-16 18:30:14.366: E/AndroidRuntime(1522): at 安卓.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1050)
11-16 18:30:14.366: E/AndroidRuntime(1522): at 安卓.app.ActivityThread.performLaunchActivity(ActivityThread.java:1960)
11-16 18:30:14.366: E/AndroidRuntime(1522): ... 11 more
testpic。xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:安卓="http://schemas.安卓.com/apk/res/安卓"
安卓:layout_width="match_parent"
安卓:layout_height="match_parent"
安卓:orientation="vertical" >
<ImageView
安卓:id="@+id/imageView"
安卓:layout_width="match_parent"
安卓:layout_height="match_parent"
安卓:src="@drawable/ic_launcher" />
</LinearLayout>
# 1 楼答案
似乎您忘记了在xml布局中添加testpic按钮id,因此在FotoMaker活动中您的按钮
btn
为空因此,在
testpic.xml
布局文件中添加id为testpic
的按钮视图