我是android新手。我正在努力解决上述错误。请帮我修复错误。我在名为＆＃34; DetailsUsers.java＆＃34;的活动中发现此错误。我的主要活动是正常运作。我点击主屏幕上的一个按钮，点击按钮后应用程序应该进入详细用户屏幕，而不是崩溃。请提供解决方案。
我的DetailsUsers.java代码：
import com.db.appform12.R;
import app.form.appform12.DatabaseHandler;
import app.form.appform12.User;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
public class DetailsUsers extends Activity implements OnClickListener{
private String position = null;
//User user = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_details_users);
Intent intent = getIntent();
position = intent.getStringExtra("position");
Log.d("value of position from intent", position);
DatabaseHandler db;
if (position !=null){
db = new DatabaseHandler(this);
}
else {
return;
}
User user = db.getUser(position);
if (user !=null) {
TextView textViewDetailName = (TextView) findViewById(R.id.textViewName);
textViewDetailName.setText(user.getName());
}
else {
return;
}
// TextView textViewDetailName = (TextView) findViewById(R.id.textViewName);
// try {
// textViewDetailName.setText(user.getName());
// }catch (Exception e) {
// System.out.print("Error is Here");
// }
TextView textViewDetailAddress = (TextView) findViewById(R.id.textViewAddress);
try {
textViewDetailAddress.setText(user.getAddress());
}catch (Exception e) {
System.out.print("Error is Here");
}
TextView textViewDetailsPhone = (TextView) findViewById(R.id.textViewPhone);
try {
textViewDetailsPhone.setText(user.getPhone());
}catch (Exception e) {
System.out.print("Error is Here");
}
TextView textViewDetailsEmail = (TextView) findViewById(R.id.textViewEmail);
try {
textViewDetailsEmail.setText(user.getEmail());
}catch (Exception e) {
System.out.print("Error is Here");
}
TextView textViewDetailsComments = (TextView) findViewById(R.id.textViewComments);
try {
textViewDetailsComments.setText(user.getComments());
}catch (Exception e) {
System.out.print("Error is Here");
}
Button backButton = (Button)findViewById(R.id.button2);
backButton.setOnClickListener(this);
Button editButton = (Button)findViewById(R.id.button1);
editButton.setOnClickListener(this);
}
public void onClick(View v) {
if(v.getId() == R.id.button2) {
Intent intent = new Intent(getApplicationContext(), ListUsers.class);
startActivity(intent);
}
else if(v.getId() == R.id.button1) {
Intent intent = new Intent(getApplicationContext(), EditUsers.class);
intent.putExtra("position", position);
startActivity(intent);
}
}
}
我的DetailsUsers.xml：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="app.form.appform12.DetailsUsers" >
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:text="@string/hello_world" />
<TextView
android:id="@+id/textViewName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textView1"
android:layout_centerHorizontal="true"
android:layout_marginTop="33dp"
android:text="@string/full_name" />
<TextView
android:id="@+id/textViewPhone"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textViewName"
android:layout_marginTop="34dp"
android:text="@string/phone_no" />
<TextView
android:id="@+id/textViewAddress"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textViewPhone"
android:layout_marginTop="62dp"
android:text="@string/postal_address" />
<TextView
android:id="@+id/textViewEmail"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textViewAddress"
android:layout_centerVertical="true"
android:text="@string/email_id" />
<TextView
android:id="@+id/textViewComments"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textViewEmail"
android:layout_marginTop="74dp"
android:text="@string/comments_feedback" />
<Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/textView1"
android:layout_alignBottom="@+id/textView1"
android:layout_alignParentLeft="true"
android:text="@string/back_btn" />
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textViewComments"
android:layout_marginTop="41dp"
android:layout_toRightOf="@+id/textViewAddress"
android:text="@string/update_btn" />
</RelativeLayout>
我的完整ADBLOGCAT追踪：
12-29 08:04:06.579: I/dalvikvm(2798): Could not find method android.view.ViewGroup.onNestedScrollAccepted, referenced from method android.support.v7.internal.widget.ActionBarOverlayLayout.onNestedScrollAccepted
12-29 08:04:06.579: W/dalvikvm(2798): VFY: unable to resolve virtual method 11352: Landroid/view/ViewGroup;.onNestedScrollAccepted (Landroid/view/View;Landroid/view/View;I)V
12-29 08:04:06.579: D/dalvikvm(2798): VFY: replacing opcode 0x6f at 0x0000
12-29 08:04:06.599: I/dalvikvm(2798): Could not find method android.view.ViewGroup.onStopNestedScroll, referenced from method android.support.v7.internal.widget.ActionBarOverlayLayout.onStopNestedScroll
12-29 08:04:06.599: W/dalvikvm(2798): VFY: unable to resolve virtual method 11358: Landroid/view/ViewGroup;.onStopNestedScroll (Landroid/view/View;)V
12-29 08:04:06.599: D/dalvikvm(2798): VFY: replacing opcode 0x6f at 0x0000
12-29 08:04:06.619: I/dalvikvm(2798): Could not find method android.support.v7.internal.widget.ActionBarOverlayLayout.stopNestedScroll, referenced from method android.support.v7.internal.widget.ActionBarOverlayLayout.setHideOnContentScrollEnabled
12-29 08:04:06.659: W/dalvikvm(2798): VFY: unable to resolve virtual method 9045: Landroid/support/v7/internal/widget/ActionBarOverlayLayout;.stopNestedScroll ()V
12-29 08:04:06.659: D/dalvikvm(2798): VFY: replacing opcode 0x6e at 0x000e
12-29 08:04:06.789: I/dalvikvm(2798): Could not find method android.content.res.TypedArray.getChangingConfigurations, referenced from method android.support.v7.internal.widget.TintTypedArray.getChangingConfigurations
12-29 08:04:06.839: W/dalvikvm(2798): VFY: unable to resolve virtual method 370: Landroid/content/res/TypedArray;.getChangingConfigurations ()I
12-29 08:04:06.839: D/dalvikvm(2798): VFY: replacing opcode 0x6e at 0x0002
12-29 08:04:06.859: I/dalvikvm(2798): Could not find method android.content.res.TypedArray.getType, referenced from method android.support.v7.internal.widget.TintTypedArray.getType
12-29 08:04:06.879: W/dalvikvm(2798): VFY: unable to resolve virtual method 392: Landroid/content/res/TypedArray;.getType (I)I
12-29 08:04:06.879: D/dalvikvm(2798): VFY: replacing opcode 0x6e at 0x0002
12-29 08:04:13.009: I/Choreographer(2798): Skipped 231 frames! The application may be doing too much work on its main thread.
12-29 08:04:13.669: D/gralloc_goldfish(2798): Emulator without GPU emulation detected.
12-29 08:04:43.579: D/AndroidRuntime(2798): Shutting down VM
12-29 08:04:43.579: W/dalvikvm(2798): threadid=1: thread exiting with uncaught exception (group=0xb0f44648)
12-29 08:04:43.639: E/AndroidRuntime(2798): FATAL EXCEPTION: main
12-29 08:04:43.639: E/AndroidRuntime(2798): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.db.appform12/app.form.appform12.DetailsUsers}: java.lang.NullPointerException: println needs a message
12-29 08:04:43.639: E/AndroidRuntime(2798): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
12-29 08:04:43.639: E/AndroidRuntime(2798): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
12-29 08:04:43.639: E/AndroidRuntime(2798): at android.app.ActivityThread.access$600(ActivityThread.java:141)
12-29 08:04:43.639: E/AndroidRuntime(2798): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
12-29 08:04:43.639: E/AndroidRuntime(2798): at android.os.Handler.dispatchMessage(Handler.java:99)
12-29 08:04:43.639: E/AndroidRuntime(2798): at android.os.Looper.loop(Looper.java:137)
12-29 08:04:43.639: E/AndroidRuntime(2798): at android.app.ActivityThread.main(ActivityThread.java:5103)
12-29 08:04:43.639: E/AndroidRuntime(2798): at java.lang.reflect.Method.invokeNative(Native Method)
12-29 08:04:43.639: E/AndroidRuntime(2798): at java.lang.reflect.Method.invoke(Method.java:525)
12-29 08:04:43.639: E/AndroidRuntime(2798): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
12-29 08:04:43.639: E/AndroidRuntime(2798): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
12-29 08:04:43.639: E/AndroidRuntime(2798): at dalvik.system.NativeStart.main(Native Method)
12-29 08:04:43.639: E/AndroidRuntime(2798): Caused by: java.lang.NullPointerException: println needs a message
12-29 08:04:43.639: E/AndroidRuntime(2798): at android.util.Log.println_native(Native Method)
12-29 08:04:43.639: E/AndroidRuntime(2798): at android.util.Log.d(Log.java:138)
12-29 08:04:43.639: E/AndroidRuntime(2798): at app.form.appform12.DetailsUsers.onCreate(DetailsUsers.java:31)
12-29 08:04:43.639: E/AndroidRuntime(2798): at android.app.Activity.performCreate(Activity.java:5133)
12-29 08:04:43.639: E/AndroidRuntime(2798): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
12-29 08:04:43.639: E/AndroidRuntime(2798): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
12-29 08:04:43.639: E/AndroidRuntime(2798): ... 11 more
12-29 08:04:43.739: D/dalvikvm(2798): GC_FOR_ALLOC freed 230K, 13% free 2739K/3148K, paused 58ms, total 73ms
12-29 08:04:49.950: I/Process(2798): Sending signal. PID: 2798 SIG: 9
我一直在努力解决这个问题。请提供建议并帮助我。提前谢谢。
答案 0 :(得分：3)
position是null。您无法将Log.d()与null消息一起使用。如果您希望使用Log.d()，请先检查position并查看它是否为null，然后记录其他内容。如果您不希望position成为null，则需要了解您的活动是如何开始的，以及您的额外费用缺失的原因或null。
答案 1 :(得分：0)
Log.d（“意图的位置值”，位置）;检查位置值是否为null如果要使用System.out.println（）;它也会创建错误;而不是System.out.print（）;