在我的Android应用程序，我在其中用户将信息分为3个editTexts 3个对话框和它会显示数据的一个到另一个类/页后，随机挑选，选择哪些数据。
这是我的mainClass
public class MainActivity extends Activity {
//Variables are displayed in this area
String choices[] = new String[3];
//EditText editText;
//EditText editText2;
//EditText editText3;
Button mainButton ;
Random rand = new Random();
int finalChoice;
String displayChoice = "";
EditText editText ;
EditText editText2;
EditText editText3;
EditText editText4;
String test;
int count = 3;
//--------------------------- --------------------------------------------------------
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Makes Button
setContentView(R.layout.activity_main);
declareTextBox();
setButton();
String choice1 = editText.getText().toString();
String choice2 = editText2.getText().toString();
String choice3 = editText3.getText().toString();
choices[0] = choice1; //pass from click button to method.
choices[1] = choice2;
choices[2] = choice3;
finalChoice =rand.nextInt(2);
}
public void setButton()
{
final Button mainbutton = (Button) findViewById(R.id.mainButton);
mainbutton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
test = ((EditText) findViewById(R.id.editText4)).getText().toString();
// count++;
//retChoice();
// loadScreen();
Intent i = new Intent(MainActivity.this, resultScreen.class);
i.putExtra("display" , displayChoice);
Intent intent = new Intent(MainActivity.this,loadingScreen.class);
//start the second Activity
MainActivity.this.startActivity(intent);
}
});
}
public void declareTextBox()
{
editText = (EditText) findViewById(R.id.editText1);
editText2 = (EditText) findViewById(R.id.editText2);
editText3 = (EditText) findViewById(R.id.editText3);
}
public void getString(String finalChoice)
{
finalChoice = displayChoice;
}
public String retChoice()
{
displayChoice = choices[finalChoice];
return displayChoice;
}
public void clearText()
{
editText.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
editText.setText(" ");
}
});
editText2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
editText2.setText(" ");
}
});
editText3.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
editText3.setText(" ");
}
});
}
public void getText2()
{
}
public void getText()
{
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
这是我的Display类：
public class resultScreen extends Activity {
MainActivity ma = new MainActivity();
//Method supposedly retrieves the string data from MainActivity Class but somehow displayed null instead.
//Find a way to keep the string variable when transfering from one class to another class.
String finalResult = ma.retChoice();
public void onCreate(Bundle resultScreen){
super.onCreate(resultScreen);
setContentView(R.layout.resultscreen);
//ma.displayChoice.toString();
String str = finalResult;
TextView text = (TextView) findViewById(R.id.textView1);
text.setText(str);
final Button backbutton = (Button) findViewById(R.id.backButton);
backbutton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v)
{
Intent intent = new Intent(resultScreen.this,MainActivity.class);
resultScreen.this.startActivity(intent);
}
});
}
}
这是我的加载屏幕右侧类单击主按钮后
public class loadingScreen extends Activity{
protected void onCreate(Bundle loadingScreen) {
// TODO Auto-generated method stub
super.onCreate(loadingScreen);
setContentView(R.layout.loadingscreen);
//If sound clip 20 sec long we don't want to carryit outside next class
// A timer thread looking for "run" method
Thread timer = new Thread()
{
public void run() {
try {
//this is how many mil sec
sleep(8000);
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
Intent intent = new Intent(loadingScreen.this, resultScreen.class);
loadingScreen.this.startActivity(intent);
loadingScreen.this.finish();
}
}
};
timer.start();
}
}
我的应用程序崩溃，几秒钟到加载屏幕当程序试图以显示在resultScreen数据。
这里是我的logcat
05-17 22:32:54.446: D/AndroidRuntime(1181): Shutting down VM
05-17 22:32:54.446: W/dalvikvm(1181): threadid=1: thread exiting with uncaught exception (group=0x40a70930)
05-17 22:32:54.636: E/AndroidRuntime(1181): FATAL EXCEPTION: main
05-17 22:32:54.636: E/AndroidRuntime(1181): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.choiceprototest/com.example.choiceprototest.resultScreen}: java.lang.NullPointerException
05-17 22:32:54.636: E/AndroidRuntime(1181): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
05-17 22:32:54.636: E/AndroidRuntime(1181): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
05-17 22:32:54.636: E/AndroidRuntime(1181): at android.app.ActivityThread.access$600(ActivityThread.java:141)
05-17 22:32:54.636: E/AndroidRuntime(1181): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
05-17 22:32:54.636: E/AndroidRuntime(1181): at android.os.Handler.dispatchMessage(Handler.java:99)
05-17 22:32:54.636: E/AndroidRuntime(1181): at android.os.Looper.loop(Looper.java:137)
05-17 22:32:54.636: E/AndroidRuntime(1181): at android.app.ActivityThread.main(ActivityThread.java:5039)
05-17 22:32:54.636: E/AndroidRuntime(1181): at java.lang.reflect.Method.invokeNative(Native Method)
05-17 22:32:54.636: E/AndroidRuntime(1181): at java.lang.reflect.Method.invoke(Method.java:511)
05-17 22:32:54.636: E/AndroidRuntime(1181): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-17 22:32:54.636: E/AndroidRuntime(1181): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-17 22:32:54.636: E/AndroidRuntime(1181): at dalvik.system.NativeStart.main(Native Method)
05-17 22:32:54.636: E/AndroidRuntime(1181): Caused by: java.lang.NullPointerException
05-17 22:32:54.636: E/AndroidRuntime(1181): at com.example.choiceprototest.MainActivity.retChoice(MainActivity.java:101)
05-17 22:32:54.636: E/AndroidRuntime(1181): at com.example.choiceprototest.resultScreen.<init>(resultScreen.java:18)
05-17 22:32:54.636: E/AndroidRuntime(1181): at java.lang.Class.newInstanceImpl(Native Method)
05-17 22:32:54.636: E/AndroidRuntime(1181): at java.lang.Class.newInstance(Class.java:1319)
05-17 22:32:54.636: E/AndroidRuntime(1181): at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
05-17 22:32:54.636: E/AndroidRuntime(1181): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
05-17 22:32:54.636: E/AndroidRuntime(1181): ... 11 more
05-17 22:33:03.385: I/Process(1181): Sending signal. PID: 1181 SIG: 9
05-17 22:33:05.435: E/Trace(1204): error opening trace file: No such file or directory (2)
多谢你们。
