问题描述
我下了Android开发人员指南使用具有更复杂的对象,我发送到不同的活动,打算在Parcelable例子。现在,我的班是一个String成员的包装。如果我把对象的意图和阅读从中读取预期,但是,在接收方的意图回来,它始终是空指针。
我的类:
包com.mobibob.android.myapp;进口android.os.Parcel;
进口android.os.Parcelable;
公共类ContentItem实现Parcelable {
公共字符串名称=名;
公共静态最后弦乐EXTRA_CONTENT_DETAIL =contentDetail; ContentItem(字符串n){
名称= N;
} ContentItem(包裹中){
in.readParcelable(ContentItem.class.getClassLoader()); < ---新的code
名称= in.readString();
} @覆盖
公共字符串的toString(){
返回name.toString();
} @覆盖
公众诠释describeContents(){
返回0;
} @覆盖
公共无效writeToParcel(DEST包裹,INT标志){
dest.writeString(名);
} 公众最终Parcelable.Creator< ContentItem> CREATOR =新Parcelable.Creator< ContentItem>(){
公共ContentItem createFromParcel(包裹中){
返回新ContentItem(中);
} 公共ContentItem [] newArray(INT大小){
返回新ContentItem【尺寸】;
}
};}
我的意图/回读/ startActivity的设置:
ContentItem CI =新ContentItem(mobibob);
//启动...
意图I =新意图(getApplicationContext(),ContentDetailActivity.class);
i.putExtra(ContentItem.EXTRA_CONTENT_DETAIL,CI);
ContentItem readbackCi = i.getParcelableExtra(ContentItem.EXTRA_CONTENT_DETAIL);
Log.d(TAG,\\ n \\ n \\ t+ readbackCi.name);
startActivity(ⅰ);
我的接收活动:
包com.mobibob.android.myapp;进口android.app.Activity;
进口android.content.Intent;
进口android.os.Bundle;
进口android.util.Log;
进口android.widget.TextView;公共类ContentDetailActivity延伸活动{ 公共静态最后的字符串标记=ContentDetailActivity; @覆盖
公共无效的onCreate(捆绑savedInstanceState){
super.onCreate(savedInstanceState);
的setContentView(R.layout.content_detail); 尝试{
意向I = getIntent();
Log.d(TAG的意图:+ i.toString());
Log.d(TAG,演员:+ i.getExtras()); ContentItem CI =(ContentItem)i.getParcelableExtra(ContentItem.EXTRA_CONTENT_DETAIL); Log.d(TAG,内容项:+ ci.toString()); ((的TextView)findViewById(R.id.name_of_content))的setText(ci.name)。 }赶上(例外五){
Log.d(TAG,e.toString());
}
}}
我的日志:
15 08-16:03:40.121 I / HomeActivity(9840):onItemClick - 适配器视图(POS = 1 ID = 1)
08-16 15:03:40.121 D / HomeActivity(9840):
08-16 15:03:40.121 D / HomeActivity(9840):
08-16 15:03:40.121 D / HomeActivity(9840):摇滚/流行
08-16 15:03:40.131 I / ActivityManager(1186):启动活动:意向{CMP = com.mobibob.android.myapp / .ContentDetailActivity(有临时演员)}
08-16 15:03:40.341 D / ContentDetailActivity(9840):意向:意向{CMP = com.mobibob.android.myapp / .ContentDetailActivity(有临时演员)}
08-16 15:03:40.341 D / ContentDetailActivity(9840):演员:捆绑[mParcelledData.dataSize = 148]
08-16 15:03:40.351 D / ContentDetailActivity(9840):显示java.lang.NullPointerException
08-16 15:03:40.653 I / ActivityManager(1186):显示活动com.mobibob.android.myapp / .ContentDetailActivity:336毫秒(总336毫秒)
我的堆栈跟踪:
08-16 17:19:52.170 I / HomeActivity(3147):onItemClick - 适配器视图(POS = 3 ID = 3)
08-16 17:19:52.170 D / HomeActivity(3147):
08-16 17:19:52.170 D / HomeActivity(3147):
08-16 17:19:52.170 D / HomeActivity(3147):mobibob
08-16 17:19:52.170 I / ActivityManager(1202):启动活动:意向{CMP = com.mobibob.android.myapp / .ContentDetailActivity(有临时演员)}
08-16 17:19:52.410 D / ContentDetailActivity(3147):意向:意向{CMP = com.mobibob.android.myapp / .ContentDetailActivity(有临时演员)}
08-16 17:19:52.410 D / ContentDetailActivity(3147):演员:捆绑[mParcelledData.dataSize = 144]
08-16 17:19:52.410 D / ContentDetailActivity(3147):显示java.lang.NullPointerException
08-16 17:19:52.410 W / System.err的(3147):显示java.lang.NullPointerException
08-16 17:19:52.420 W / System.err的(3147):在java.lang.reflect.Field.getField(本机方法)
08-16 17:19:52.420 W / System.err的(3147):在java.lang.reflect.Field.get(Field.java:247)
08-16 17:19:52.420 W / System.err的(3147):在android.os.Parcel.readParcelable(Parcel.java:1811)
08-16 17:19:52.420 W / System.err的(3147):在android.os.Parcel.readValue(Parcel.java:1713)
08-16 17:19:52.420 W / System.err的(3147):在android.os.Parcel.readMapInternal(Parcel.java:1947)
08-16 17:19:52.420 W / System.err的(3147):在android.os.Bundle.unparcel(Bundle.java:169)
08-16 17:19:52.420 W / System.err的(3147):在android.os.Bundle.getParcelable(Bundle.java:1037)
08-16 17:19:52.430 W / System.err的(3147):在android.content.Intent.getParcelableExtra(Intent.java:3276)
08-16 17:19:52.430 W / System.err的(3147):在com.mobibob.android.myapp.ContentDetailActivity.onCreate(ContentDetailActivity.java:24)
08-16 17:19:52.430 W / System.err的(3147):在android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-16 17:19:52.430 W / System.err的(3147):在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459)
08-16 17:19:52.430 W / System.err的(3147):在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
08-16 17:19:52.430 W / System.err的(3147):在android.app.ActivityThread.access $ 2200(ActivityThread.java:119)
08-16 17:19:52.430 W / System.err的(3147):在android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1863)
08-16 17:19:52.430 W / System.err的(3147):在android.os.Handler.dispatchMessage(Handler.java:99)
08-16 17:19:52.430 W / System.err的(3147):在android.os.Looper.loop(Looper.java:123)
08-16 17:19:52.430 W / System.err的(3147):在android.app.ActivityThread.main(ActivityThread.java:4363)
08-16 17:19:52.430 W / System.err的(3147):在java.lang.reflect.Method.invokeNative(本机方法)
08-16 17:19:52.430 W / System.err的(3147):在java.lang.reflect.Method.invoke(Method.java:521)
08-16 17:19:52.430 W / System.err的(3147):在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:868)
08-16 17:19:52.430 W / System.err的(3147):在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
08-16 17:19:52.440 W / System.err的(3147):在dalvik.system.NativeStart.main(本机方法)
08-16 17:19:52.895 I / ActivityManager(1202):显示活动com.mobibob.android.myapp / .ContentDetailActivity:582毫秒(总582毫秒)
我猜 in.readParcelable(ContentItem.class.getClassLoader());
已返回您重新ContentItem。所以,你应该把这些线成Parcelable.Creator的createFromParcel法。
只是一个猜测,但。
I am following the Parcelable example in the Android developer guide with the intention of having a more complex object that I send to different activities. Right now, my class is a wrapper of a String member. If I put the object in the intent and read it back from the Intent it reads as expected, however, on the receiver side, it is always null-pointer.
My class:
package com.mobibob.android.myapp;
import android.os.Parcel;
import android.os.Parcelable;
public class ContentItem implements Parcelable {
public String name = "name";
public static final String EXTRA_CONTENT_DETAIL = "contentDetail";
ContentItem(String n) {
name = n;
}
ContentItem(Parcel in) {
in.readParcelable(ContentItem.class.getClassLoader()); <--- NEW CODE
name = in.readString();
}
@Override
public String toString() {
return name.toString();
}
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(name);
}
public final Parcelable.Creator<ContentItem> CREATOR = new Parcelable.Creator<ContentItem>() {
public ContentItem createFromParcel(Parcel in) {
return new ContentItem(in);
}
public ContentItem[] newArray(int size) {
return new ContentItem[size];
}
};
}
My setup of intent / read-back / startActivity:
ContentItem ci = new ContentItem("mobibob");
// Launch ...
Intent i = new Intent(getApplicationContext(), ContentDetailActivity.class);
i.putExtra(ContentItem.EXTRA_CONTENT_DETAIL, ci);
ContentItem readbackCi = i.getParcelableExtra(ContentItem.EXTRA_CONTENT_DETAIL);
Log.d(TAG, "\n\n\t" + readbackCi.name);
startActivity(i);
My receiving activity:
package com.mobibob.android.myapp;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
public class ContentDetailActivity extends Activity {
public static final String TAG = "ContentDetailActivity";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.content_detail);
try {
Intent i = getIntent();
Log.d(TAG, "intent: " + i.toString());
Log.d(TAG, "extras: " + i.getExtras());
ContentItem ci = (ContentItem) i.getParcelableExtra(ContentItem.EXTRA_CONTENT_DETAIL);
Log.d(TAG, "content-item: " + ci.toString());
((TextView) findViewById(R.id.name_of_content)).setText(ci.name);
} catch (Exception e) {
Log.d(TAG, e.toString());
}
}
}
My log:
08-16 15:03:40.121 I/HomeActivity( 9840): onItemClick - AdapterView (pos=1 id=1)
08-16 15:03:40.121 D/HomeActivity( 9840):
08-16 15:03:40.121 D/HomeActivity( 9840):
08-16 15:03:40.121 D/HomeActivity( 9840): Rock/Pop
08-16 15:03:40.131 I/ActivityManager( 1186): Starting activity: Intent { cmp=com.mobibob.android.myapp/.ContentDetailActivity (has extras) }
08-16 15:03:40.341 D/ContentDetailActivity( 9840): intent: Intent { cmp=com.mobibob.android.myapp/.ContentDetailActivity (has extras) }
08-16 15:03:40.341 D/ContentDetailActivity( 9840): extras: Bundle[mParcelledData.dataSize=148]
08-16 15:03:40.351 D/ContentDetailActivity( 9840): java.lang.NullPointerException
08-16 15:03:40.653 I/ActivityManager( 1186): Displayed activity com.mobibob.android.myapp/.ContentDetailActivity: 336 ms (total 336 ms)
My stack backtrace:
08-16 17:19:52.170 I/HomeActivity( 3147): onItemClick - AdapterView (pos=3 id=3)
08-16 17:19:52.170 D/HomeActivity( 3147):
08-16 17:19:52.170 D/HomeActivity( 3147):
08-16 17:19:52.170 D/HomeActivity( 3147): mobibob
08-16 17:19:52.170 I/ActivityManager( 1202): Starting activity: Intent { cmp=com.mobibob.android.myapp/.ContentDetailActivity (has extras) }
08-16 17:19:52.410 D/ContentDetailActivity( 3147): intent: Intent { cmp=com.mobibob.android.myapp/.ContentDetailActivity (has extras) }
08-16 17:19:52.410 D/ContentDetailActivity( 3147): extras: Bundle[mParcelledData.dataSize=144]
08-16 17:19:52.410 D/ContentDetailActivity( 3147): java.lang.NullPointerException
08-16 17:19:52.410 W/System.err( 3147): java.lang.NullPointerException
08-16 17:19:52.420 W/System.err( 3147): at java.lang.reflect.Field.getField(Native Method)
08-16 17:19:52.420 W/System.err( 3147): at java.lang.reflect.Field.get(Field.java:247)
08-16 17:19:52.420 W/System.err( 3147): at android.os.Parcel.readParcelable(Parcel.java:1811)
08-16 17:19:52.420 W/System.err( 3147): at android.os.Parcel.readValue(Parcel.java:1713)
08-16 17:19:52.420 W/System.err( 3147): at android.os.Parcel.readMapInternal(Parcel.java:1947)
08-16 17:19:52.420 W/System.err( 3147): at android.os.Bundle.unparcel(Bundle.java:169)
08-16 17:19:52.420 W/System.err( 3147): at android.os.Bundle.getParcelable(Bundle.java:1037)
08-16 17:19:52.430 W/System.err( 3147): at android.content.Intent.getParcelableExtra(Intent.java:3276)
08-16 17:19:52.430 W/System.err( 3147): at com.mobibob.android.myapp.ContentDetailActivity.onCreate(ContentDetailActivity.java:24)
08-16 17:19:52.430 W/System.err( 3147): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-16 17:19:52.430 W/System.err( 3147): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459)
08-16 17:19:52.430 W/System.err( 3147): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
08-16 17:19:52.430 W/System.err( 3147): at android.app.ActivityThread.access$2200(ActivityThread.java:119)
08-16 17:19:52.430 W/System.err( 3147): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)
08-16 17:19:52.430 W/System.err( 3147): at android.os.Handler.dispatchMessage(Handler.java:99)
08-16 17:19:52.430 W/System.err( 3147): at android.os.Looper.loop(Looper.java:123)
08-16 17:19:52.430 W/System.err( 3147): at android.app.ActivityThread.main(ActivityThread.java:4363)
08-16 17:19:52.430 W/System.err( 3147): at java.lang.reflect.Method.invokeNative(Native Method)
08-16 17:19:52.430 W/System.err( 3147): at java.lang.reflect.Method.invoke(Method.java:521)
08-16 17:19:52.430 W/System.err( 3147): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
08-16 17:19:52.430 W/System.err( 3147): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
08-16 17:19:52.440 W/System.err( 3147): at dalvik.system.NativeStart.main(Native Method)
08-16 17:19:52.895 I/ActivityManager( 1202): Displayed activity com.mobibob.android.myapp/.ContentDetailActivity: 582 ms (total 582 ms)
I'd guess that in.readParcelable(ContentItem.class.getClassLoader());
returns already your recreated ContentItem. So you should put that line into the createFromParcel-Method in Parcelable.Creator. Just a guess though.
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