我试图在两个活动之间传递几个值但是我的代码崩溃了，我不明白为什么。从图像按钮调用代码，但应用程序停止。
if(v==image1){
try {
Calendar c = Calendar.getInstance();
System.out.println("Current time => "+c.getTime());
SimpleDateFormat df = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
String formattedDate = df.format(c.getTime());
//now we have the time lets write it to the file
File myFile = new File("/sdcard/.working/mx.txt");
myFile.createNewFile();
FileOutputStream fOut = new FileOutputStream(myFile, true);
OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
myOutWriter.append(formattedDate);
myOutWriter.append(" :");
myOutWriter.append(tv1.getText());
myOutWriter.append(" , ");
myOutWriter.close();
fOut.close();
}catch (Exception e) {
Toast.makeText(getBaseContext(), e.getMessage(), Toast.LENGTH_SHORT).show();
}
mx=mx++;
Intent startabout = new Intent(RTO.this, RTOShooting.class); //this is about screen
startabout.putExtra("mx", mx);
startabout.putExtra("Callsign", tv1.getText());
final int result=1;
startActivityForResult(startabout, result);
overridePendingTransition(R.anim.zoom_enter, R.anim.zoom_exit);
}
接收代码看起来像这样（不是说我到目前为止......）
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_rtoshooting);
Bundle extras = getIntent().getExtras();
if (extras !=null){
int mx = extras.getInt("mx");
}
}
有人可以引导我去找我明显遗失的东西吗？
LOGCAT输出
02-27 11:44:46.461: W/dalvikvm(20231): threadid=1: thread exiting with uncaught exception (group=0x41053930)
02-27 11:44:46.471: E/AndroidRuntime(20231): FATAL EXCEPTION: main
02-27 11:44:46.471: E/AndroidRuntime(20231): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.nexgen.threedashone.trainer/com.nexgen.threedashone.trainer.RTOShooting}: java.lang.NullPointerException
02-27 11:44:46.471: E/AndroidRuntime(20231): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2304)
02-27 11:44:46.471: E/AndroidRuntime(20231): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2354)
02-27 11:44:46.471: E/AndroidRuntime(20231): at android.app.ActivityThread.access$600(ActivityThread.java:150)
02-27 11:44:46.471: E/AndroidRuntime(20231): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1244)
02-27 11:44:46.471: E/AndroidRuntime(20231): at android.os.Handler.dispatchMessage(Handler.java:99)
02-27 11:44:46.471: E/AndroidRuntime(20231): at android.os.Looper.loop(Looper.java:137)
02-27 11:44:46.471: E/AndroidRuntime(20231): at android.app.ActivityThread.main(ActivityThread.java:5191)
02-27 11:44:46.471: E/AndroidRuntime(20231): at java.lang.reflect.Method.invokeNative(Native Method)
02-27 11:44:46.471: E/AndroidRuntime(20231): at java.lang.reflect.Method.invoke(Method.java:511)
02-27 11:44:46.471: E/AndroidRuntime(20231): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
02-27 11:44:46.471: E/AndroidRuntime(20231): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
02-27 11:44:46.471: E/AndroidRuntime(20231): at dalvik.system.NativeStart.main(Native Method)
02-27 11:44:46.471: E/AndroidRuntime(20231): Caused by: java.lang.NullPointerException
02-27 11:44:46.471: E/AndroidRuntime(20231): at com.nexgen.threedashone.trainer.RTOShooting.onCreate(RTOShooting.java:40)
02-27 11:44:46.471: E/AndroidRuntime(20231): at android.app.Activity.performCreate(Activity.java:5104)
02-27 11:44:46.471: E/AndroidRuntime(20231): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
02-27 11:44:46.471: E/AndroidRuntime(20231): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2258)
02-27 11:44:46.471: E/AndroidRuntime(20231): ... 11 more
我也试过像这样创建自己的包：
Bundle b = new Bundle();
b.putString("Callsign", tv1.getText().toString());
b.putInt("mx", mx);
startabout.putExtras(b);
像这样收到：
Bundle b = getIntent().getExtras();
String callsign = b.getString("Callsign");
int mx = b.getInt("mx");
但它仍然与非常相似的logcat输出崩溃。 tvcallsign.setText（呼号）;
编辑：这是每个活动的完整代码，它不漂亮，但我刚刚进入java和android： package com.test.trainer;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.List;
import android.os.Bundle;
import android.app.Activity;
import android.content.ContextWrapper;
import android.content.Intent;
import android.content.res.AssetManager;
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.Chronometer;
import android.widget.ImageButton;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import android.support.v4.app.NavUtils;
public class RTO extends Activity implements Chronometer.OnChronometerTickListener, OnClickListener {
//define buttons etc
private Button babout;
private Button bhome;
private ImageButton image1;
private ImageButton image2;
private ImageButton image3;
private ImageButton image4;
private ImageButton image5;
private ImageButton image6;
private ImageButton image7;
private ImageButton image8;
private ImageButton image9;
private ImageButton image10;
private ImageButton image11;
private ImageButton image12;
private ImageButton image13;
private ImageButton image14;
private ImageButton image15;
private ImageButton image16;
private ImageButton imagesetup;
private ImageButton imageevent;
private ImageButton imageend;
TextView tv1;
TextView tv2;
TextView tv3;
TextView tv4;
TextView tv5;
TextView tv6;
TextView tv7;
TextView tv8;
TextView tv9;
TextView tv10;
TextView tv11;
TextView tv12;
TextView tv13;
TextView tv14;
TextView tv15;
TextView tv16;
public ListView lv1;
public Chronometer mchrono;
//define logic
public int mx = 0;
public int configured = 0;
public int side = 0; //int to handle which colour buttons to use
public int prijettype = 0; //int for primary type
public int secjettype = 0; //int for sec type
public int prijetnumber = 0; //int for primary numbers
public int secjetnumber = 0; //int for sec numbers
//hint array strings
public String loadeddata;
public String[] splitdata;
public String callsign;
ContextWrapper mContext = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_rto);
getActionBar().setDisplayHomeAsUpEnabled(true);
//define the buttons etc for use
babout = (Button)findViewById(R.id.babout); //about button
bhome = (Button)findViewById(R.id.bhome); //home button
image1 = (ImageButton)findViewById(R.id.image1);
image2 = (ImageButton)findViewById(R.id.image2);
image3 = (ImageButton)findViewById(R.id.image3);
image4 = (ImageButton)findViewById(R.id.image4);
image5 = (ImageButton)findViewById(R.id.image5);
image6 = (ImageButton)findViewById(R.id.image6);
image7 = (ImageButton)findViewById(R.id.image7);
image8 = (ImageButton)findViewById(R.id.image8);
image9 = (ImageButton)findViewById(R.id.image9);
image10 = (ImageButton)findViewById(R.id.image10);
image11 = (ImageButton)findViewById(R.id.image11);
image12 = (ImageButton)findViewById(R.id.image12);
image13 = (ImageButton)findViewById(R.id.image13);
image14 = (ImageButton)findViewById(R.id.image14);
image15 = (ImageButton)findViewById(R.id.image15);
image16 = (ImageButton)findViewById(R.id.image16);
imageend = (ImageButton)findViewById(R.id.imageend); //end mission
imagesetup = (ImageButton)findViewById(R.id.imagesetup); //setup button
imageevent = (ImageButton)findViewById(R.id.imageevent); //event button
tv1 = (TextView) findViewById(R.id.tv1);
tv2 = (TextView) findViewById(R.id.tv2);
tv3 = (TextView) findViewById(R.id.tv3);
tv4 = (TextView) findViewById(R.id.tv4);
tv5 = (TextView) findViewById(R.id.tv5);
tv6 = (TextView) findViewById(R.id.tv6);
tv7 = (TextView) findViewById(R.id.tv7);
tv8 = (TextView) findViewById(R.id.tv8);
tv9 = (TextView) findViewById(R.id.tv9);
tv10 = (TextView) findViewById(R.id.tv10);
tv11 = (TextView) findViewById(R.id.tv11);
tv12 = (TextView) findViewById(R.id.tv12);
tv13 = (TextView) findViewById(R.id.tv13);
tv14 = (TextView) findViewById(R.id.tv14);
tv15 = (TextView) findViewById(R.id.tv15);
tv16 = (TextView) findViewById(R.id.tv16);
image1.setOnClickListener(this);
image2.setOnClickListener(this);
image3.setOnClickListener(this);
image4.setOnClickListener(this);
image5.setOnClickListener(this);
image6.setOnClickListener(this);
image7.setOnClickListener(this);
image8.setOnClickListener(this);
image9.setOnClickListener(this);
image10.setOnClickListener(this);
image11.setOnClickListener(this);
image12.setOnClickListener(this);
image13.setOnClickListener(this);
image14.setOnClickListener(this);
image15.setOnClickListener(this);
image16.setOnClickListener(this);
imageend.setOnClickListener(this);
imagesetup.setOnClickListener(this);
imageevent.setOnClickListener(this);
settextviews();
setimageviews();
hidethem();
arrayload();
}//end oncreate
public void arrayload() {
}
public void settextviews() {
//load the asset files themselves
StringBuilder text = new StringBuilder();
try {
BufferedReader br = new BufferedReader(new FileReader("/sdcard/NexGen/RTOLOGS/.working/1.txt"));
String line;
while ((line = br.readLine()) != null) {
text.append(line);
text.append('\n');
}
//set the text we recovered to the TextView
tv1.setText(text);
//load progress info
StringBuilder text2 = new StringBuilder();
BufferedReader br2 = new BufferedReader(new FileReader("/sdcard/NexGen/RTOLOGS/.working/2.txt"));
String line2;
while ((line2 = br2.readLine()) != null) {
text2.append(line2);
text2.append('\n');
}
tv2.setText(new String(text2));
} //end try
catch (IOException ex) {
return;
}
public void setimageviews() {
//nothing here yet
}
public void hidethem() {
//nothing here yet
}
public void onClick(View v) {
// TODO Auto-generated method stub
if (v==bhome) {
// TODO Auto-generated method stub
Intent starthome = new Intent(RTO.this, Main.class); //this is about screen
startActivity(starthome);
overridePendingTransition(R.anim.zoom_enter, R.anim.zoom_exit);
}
if (v==babout) {
Intent startabout = new Intent(RTO.this, AboutScreen.class); //this is about screen
startActivity(startabout);
overridePendingTransition(R.anim.zoom_enter, R.anim.zoom_exit);
}
if(v==image1){
mx=mx++;
try {
Calendar c = Calendar.getInstance();
System.out.println("Current time => "+c.getTime());
SimpleDateFormat df = new SimpleDateFormat("HH:mm:ss");
String formattedDate = df.format(c.getTime());
//now we have the time lets write it to the file
String fileName = String.valueOf(mx) +".txt";
File myFile = new File("/sdcard/test/LOGS/.working/mx/" +fileName);
myFile.createNewFile();
FileOutputStream fOut = new FileOutputStream(myFile, true);
OutputStreamWriter myOutWriter =
new OutputStreamWriter(fOut);
myOutWriter.append(formattedDate);
myOutWriter.append(" :");
myOutWriter.append(tv1.getText());
myOutWriter.append(" , ");
myOutWriter.close();
fOut.close();
}
catch (Exception e) {
Toast.makeText(getBaseContext(), e.getMessage(),
Toast.LENGTH_SHORT).show();
}
Bundle b = new Bundle();
String callsign = (String)tv1.getText().toString();
b.putString("Callsign", callsign);
b.putInt("mx", mx);
Intent startabout = new Intent(RTO.this, RTOShooting.class); //this is next screen
startabout.putExtras(b);
startActivity(startabout);
overridePendingTransition(R.anim.zoom_enter, R.anim.zoom_exit);
}
} //end onClick
//nothing below here yet
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_rto, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
public void onChronometerTick(Chronometer chronometer) {
// TODO Auto-generated method stub
}
}
接收活动如下所示：
package com.test.trainer;
import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStreamWriter;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ImageButton;
import android.widget.TextView;
import android.widget.Toast;
public class RTOShooting extends Activity implements OnClickListener {
private ImageButton image1;
private ImageButton image2;
private ImageButton image3;
private ImageButton image3close;
private ImageButton image3medium;
private ImageButton image3short;
public int MX;
TextView tvcallsign;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_rtoshooting);
Bundle b = getIntent().getExtras();
String callsign = b.getString("Callsign");
int mx = b.getInt("mx");
MX = mx;
tvcallsign.setText(callsign);
tvcallsign = (TextView) findViewById(R.id.tvcallsign);
} //end on create
public void onClick(View v) {
// TODO Auto-generated method stub
if (v==image1) {
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_rtoshooting, menu);
return true;
}
答案 0 :(得分：0)
假设您的代码与StackTrace对齐，您会在跟踪中看到以下行：
at com.nexgen.threedashone.trainer.RTOShooting.onCreate（RTOShooting.java:40）
简单地计算RTOShooting中的行我最终在这里：
tvcallsign.setText(callsign);
tvcallsign = (TextView) findViewById(R.id.tvcallsign);
您正尝试在下一行设置您要查找的对象的文本。交换它们，一切都应该顺利。