我正在尝试创建一个应用程序，在整个高尔夫游戏中跟踪统计数据，并在必要时生成适合您的高尔夫游戏的提示。我通过将它们放入数组列表来跟踪这些漏洞。我发现你可以使用谷歌GSON在活动之间传递对象，我遵循了教程，但我觉得活动之间的数组传递最终导致了NPE，但我不确定。
11-04 11:06:02.218: E/Trace(774): error opening trace file: No such file or directory (2)
11-04 11:06:02.949: D/dalvikvm(774): GC_FOR_ALLOC freed 77K, 2% free 10958K/11143K, paused 46ms, total 48ms
11-04 11:06:03.048: D/dalvikvm(774): GC_CONCURRENT freed 168K, 3% free 11241K/11527K, paused >25ms+5ms, total 65ms
11-04 11:06:03.058: D/dalvikvm(774): WAIT_FOR_CONCURRENT_GC blocked 29ms
11-04 11:06:03.448: D/gralloc_goldfish(774): Emulator without GPU emulation detected.
11-04 11:06:06.168: D/AndroidRuntime(774): Shutting down VM
11-04 11:06:06.168: W/dalvikvm(774): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
11-04 11:06:06.208: E/AndroidRuntime(774): FATAL EXCEPTION: main
11-04 11:06:06.208: E/AndroidRuntime(774): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.testapp/com.example.testapp.StatActivity}: java.lang.NullPointerException
11-04 11:06:06.208: E/AndroidRuntime(774): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
11-04 11:06:06.208: E/AndroidRuntime(774): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
11-04 11:06:06.208: E/AndroidRuntime(774): at android.app.ActivityThread.access$600(ActivityThread.java:130)
11-04 11:06:06.208: E/AndroidRuntime(774): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
11-04 11:06:06.208: E/AndroidRuntime(774): at android.os.Handler.dispatchMessage(Handler.java:99)
11-04 11:06:06.208: E/AndroidRuntime(774): at android.os.Looper.loop(Looper.java:137)
11-04 11:06:06.208: E/AndroidRuntime(774): at android.app.ActivityThread.main(ActivityThread.java:4745)
11-04 11:06:06.208: E/AndroidRuntime(774): at java.lang.reflect.Method.invokeNative(Native Method)
11-04 11:06:06.208: E/AndroidRuntime(774): at java.lang.reflect.Method.invoke(Method.java:511)
11-04 11:06:06.208: E/AndroidRuntime(774): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
11-04 11:06:06.208: E/AndroidRuntime(774): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-04 11:06:06.208: E/AndroidRuntime(774): at dalvik.system.NativeStart.main(Native Method)
11-04 11:06:06.208: E/AndroidRuntime(774): Caused by: java.lang.NullPointerException
11-04 11:06:06.208: E/AndroidRuntime(774): at android.app.Activity.findViewById(Activity.java:1825)
11-04 11:06:06.208: E/AndroidRuntime(774): at com.example.testapp.StatActivity.<init>(StatActivity.java:38)
11-04 11:06:06.208: E/AndroidRuntime(774): at java.lang.Class.newInstanceImpl(Native Method)
11-04 11:06:06.208: E/AndroidRuntime(774): at java.lang.Class.newInstance(Class.java:1319)
11-04 11:06:06.208: E/AndroidRuntime(774): at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
11-04 11:06:06.208: E/AndroidRuntime(774): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
11-04 11:06:06.208: E/AndroidRuntime(774): ... 11 more
11-04 11:06:06.388: D/dalvikvm(774): GC_CONCURRENT freed 266K, 4% free 11366K/11719K, paused >17ms+64ms, total 142ms
11-04 11:11:06.349: I/Process(774): Sending signal. PID: 774 SIG: 9
package com.example.testapp;
import java.util.ArrayList;
import java.util.List;
import com.example.testapp.StatActivity;
import com.example.testapp.CustomOnItemSelectedListener;
import com.example.testapp.R;
import com.google.gson.Gson;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.Toast;
public class StatActivity extends Activity implements OnClickListener {
private Spinner driving_spinner;
private Spinner approach_spinner;
private Spinner chipping_spinner;
private Spinner sandshot_spinner;
private Spinner putting_spinner;
private int hole = 1;
private boolean driving_spinner_selected = false;
private boolean approach_spinner_selected = false;
private boolean chipping_spinner_selected = false;
private boolean sandshot_spinner_selected = false;
private boolean putting_spinner_selected = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_stat);
Button homeButton = (Button) findViewById(R.id.homeButton);
Button helpButton = (Button) findViewById(R.id.helpButton);
Button nextHoleButton = (Button) findViewById(R.id.nextHoleButton);
driving_spinner = (Spinner) findViewById(R.id.drivingSpinner);
approach_spinner = (Spinner) findViewById(R.id.approachSpinner);
chipping_spinner = (Spinner) findViewById(R.id.chippingSpinner);
sandshot_spinner = (Spinner) findViewById(R.id.sandShotSpinner);
putting_spinner = (Spinner) findViewById(R.id.puttingSpinner);
nextHoleButton.setOnClickListener(this);
helpButton.setOnClickListener(this);
homeButton.setOnClickListener(this);
addItemsToDrivingSpinner();
addItemsToChippingSpinner();
addItemsToPuttingSpinner();
addItemsToApproachSpinner();
addItemsToSandShotSpinner();
addListenerOnDrivingSpinnerItemSelection();
addListenerOnChippingSpinnerItemSelection();
addListenerOnPuttingSpinnerItemSelection();
addListenerOnApproachSpinnerItemSelection();
addListenerOnSandShotSpinnerItemSelection();
}
Gson gS = new Gson();
String src = getIntent().getStringExtra("round");
Round round = gS.fromJson(src, Round.class);
// add items into spinner dynamically
public void addItemsToDrivingSpinner() {
List<String> list = new ArrayList<String>();
list.add("Left");
list.add("Right");
list.add("Fairway Hit");
list.add("Par Three");
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, list);
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
driving_spinner.setAdapter(dataAdapter);
}
public void addItemsToApproachSpinner() {
List<String> list = new ArrayList<String>();
list.add("Left");
list.add("Right");
list.add("Short");
list.add("Long");
list.add("Green Hit");
list.add("No Oppurtunity");
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, list);
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
approach_spinner.setAdapter(dataAdapter);
}
public void addItemsToChippingSpinner() {
List<String> list = new ArrayList<String>();
list.add("Yes Up and Down");
list.add("No Up and Down");
list.add("No Oppurtunity");
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, list);
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
chipping_spinner.setAdapter(dataAdapter);
}
public void addItemsToSandShotSpinner() {
List<String> list = new ArrayList<String>();
list.add("Yes Sand Save");
list.add("No Sand Save");
list.add("No Oppurtunity");
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, list);
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
sandshot_spinner.setAdapter(dataAdapter);
}
public void addItemsToPuttingSpinner() {
List<String> list = new ArrayList<String>();
list.add("0");
list.add("1");
list.add("2");
list.add("3");
list.add("4");
list.add("5+");
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, list);
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
putting_spinner.setAdapter(dataAdapter);
}
public void addListenerOnDrivingSpinnerItemSelection() {
driving_spinner.setOnItemSelectedListener(new CustomOnItemSelectedListener());
driving_spinner_selected = true;
}
public void addListenerOnApproachSpinnerItemSelection() {
approach_spinner.setOnItemSelectedListener(new CustomOnItemSelectedListener());
approach_spinner_selected = true;
}
public void addListenerOnChippingSpinnerItemSelection() {
chipping_spinner.setOnItemSelectedListener(new CustomOnItemSelectedListener());
chipping_spinner_selected = true;
}
public void addListenerOnPuttingSpinnerItemSelection() {
putting_spinner.setOnItemSelectedListener(new CustomOnItemSelectedListener());
putting_spinner_selected = true;
}
public void addListenerOnSandShotSpinnerItemSelection() {
sandshot_spinner.setOnItemSelectedListener(new CustomOnItemSelectedListener());
sandshot_spinner_selected = true;
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.stat, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public void onClick(View v) {
if(v.getId() == R.id.homeButton){
Intent intent = new Intent(getApplicationContext(), HomeActivity.class);
startActivity(intent);
}else if(v.getId() == R.id.helpButton){
Intent intent = new Intent(getApplicationContext(), InstructionsActivity.class);
startActivity(intent);
}else if(v.getId() == R.id.nextHoleButton){
boolean filledIn = false;
if(driving_spinner_selected && chipping_spinner_selected && putting_spinner_selected && sandshot_spinner_selected && approach_spinner_selected)
filledIn = true;
if(filledIn) {
hole++;
round.setStats(String.valueOf(driving_spinner.getSelectedItem()),String.valueOf(putting_spinner.getSelectedItem()),String.valueOf(sandshot_spinner.getSelectedItem()),String.valueOf(chipping_spinner.getSelectedItem()),String.valueOf(approach_spinner.getSelectedItem()),hole);
Intent intent = new Intent(getApplicationContext(), StatActivity.class);
String target = gS.toJson(round);
intent.putExtra("round", target);
if(round.needTip()) {
String tip = round.generateTip();
Toast.makeText(StatActivity.this,
tip,
Toast.LENGTH_LONG).show();
}
startActivity(intent);
}
else {
Toast.makeText(StatActivity.this,
"Please fill in all statistics before continuing.",
Toast.LENGTH_SHORT).show();
}
}
}
}
package com.example.testapp;
import com.google.gson.Gson;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class HomeActivity extends Activity implements OnClickListener{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
Button startRoundButton = (Button) findViewById(R.id.startRoundButton);
Button homeHelpButton = (Button) findViewById(R.id.homeHelpButton);
homeHelpButton.setOnClickListener(this);
startRoundButton.setOnClickListener(this);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.home, menu);
return true;
}
public void onClick(View v)
{
if(v.getId() == R.id.startRoundButton){
Round round = new Round();
Intent i = new Intent(getApplicationContext(),StatActivity.class);
Gson gS = new Gson();
String target = gS.toJson(round);
i.putExtra("round", target);
startActivity(i);
}else if(v.getId() == R.id.homeHelpButton){
Intent intent = new Intent(getApplicationContext(), InstructionsActivity.class);
startActivity(intent);
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.testapp"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".HomeActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".StatActivity"
android:label="@string/title_activity_stat" >
</activity>
<activity
android:name=".InstructionsActivity"
android:label="@string/title_activity_instructions" >
</activity>
</application>
</manifest>
<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:background="@drawable/here_link"
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="com.example.testapp.StatActivity" >
<Spinner
android:id="@+id/puttingSpinner"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/approachSpinner"
android:layout_alignLeft="@+id/approachSpinner"
android:entries="@array/puttArr"
android:prompt="@string/putting" />
<Button
android:id="@+id/nextHoleButton"
android:layout_width="150dp"
android:layout_height="100dp"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:background="@drawable/next_button_background" />
<Spinner
android:id="@+id/approachSpinner"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/sandShotSpinner"
android:layout_alignLeft="@+id/sandShotSpinner"
android:entries="@array/approachArr"
android:prompt="@string/aproach" />
<Spinner
android:id="@+id/sandShotSpinner"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/nextHoleButton"
android:layout_alignLeft="@+id/drivingSpinner"
android:layout_marginBottom="19dp"
android:entries="@array/sandShotArr"
android:prompt="@string/sand_shot" />
<Spinner
android:id="@+id/drivingSpinner"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/puttingSpinner"
android:layout_centerHorizontal="true"
android:entries="@array/drivingArr"
android:prompt="@string/driving" />
<Button
android:id="@+id/helpButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="@+id/sandShotSpinner"
android:layout_alignTop="@+id/homeButton"
android:text="@string/help" />
<Button
android:id="@+id/homeButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/nextHoleButton"
android:layout_alignParentLeft="true"
android:text="@string/home" />
<Spinner
android:id="@+id/chippingSpinner"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_alignRight="@+id/drivingSpinner"
android:entries="@array/chippingArr"
android:prompt="@array/chippingArr" />
</RelativeLayout>
在打开应用程序（有效）时启动Home活动，然后在单击Start round按钮时启动stat活动，这是应用程序停止时的状态。 任何想法或想法都会有所帮助。谢谢！
答案 0 :(得分：1)
这一行
String src = getIntent().getStringExtra("round");
是你的问题。当它被调用时，没有意图获得。
需要意图的所有设置都需要在onCreate()内完成，此时意图可用。您的代码正在构建时运行，这太早了。
您还没有真正提供足够的信息来确定这是否会产生您正在制作的NPE，但它确实需要修复，即使它有＆＃39 ;还有其他错误。