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如何在一個活動中使用一個java類，我的意思是將這個活動的不同組件分散在一堆java類中。我有點新的Android和這是我到目前爲止已經試過：如何在一個活動中使用java類？
MainActivity.java
package com.example.alex.myapplication;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new Something(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.menu_main, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
Something.java
import android.view.View;
import android.widget.EditText;
import android.widget.Button;
import android.app.Activity;
public class Something {
private Activity activity;
private Button add,subtract,multiply,devide;
private EditText editA, editB, editC;
private double doubleA,doubleB,doubleC;
public Something(Activity a){
activity=a;
click();
}
public void click(){
editA = (EditText) activity.findViewById(R.id.editText);
editB = (EditText) activity.findViewById(R.id.editText2);
editC = (EditText) activity.findViewById(R.id.editText3);
doubleA =Double.parseDouble(editA.getText().toString());
doubleB =Double.parseDouble(editB.getText().toString());
add = (Button) activity.findViewById(R.id.add);
subtract = (Button) activity.findViewById(R.id.subtract);
multiply = (Button) activity.findViewById(R.id.multiply);
devide = (Button) activity.findViewById(R.id.devide);
add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
doubleC = doubleA+doubleB;
String s = "" + doubleC;
editC.setText(s);
}
});
subtract.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
doubleC = doubleA-doubleB;
String s = "" + doubleC;
editC.setText(s);
}
});
multiply.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
doubleC = doubleA*doubleB;
String s = "" + doubleC;
editC.setText(s);
}
});
devide.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
doubleC = doubleA/doubleB;
String s = "" + doubleC;
editC.setText(s);
}
});
}
}
所以我不確定爲什麼我的聽衆不在我的按鈕上工作，所以我嘗試將活動傳遞給該類聽衆添加到按鈕，但實際上現在不工作，現在我的應用程序甚至不會在模擬器中啓動。我想要做的就是讓「MainActivity」處理「Gui」，並讓「Something」類處理聽衆，但無論我做什麼，我都無法讓他們彼此通信以形成一個Activity。
logcat的
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.Activity.findViewById(Activity.java:2071)
at com.example.alex.myapplication.Something.click(Something.java:32)
at com.example.alex.myapplication.MainActivity.onCreate(MainActivity.java:19)
at android.app.Activity.performCreate(Activity.java:5937)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
at android.app.ActivityThread.performLaunchActivity
(ActivityThread.java:2251)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run (ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
*如果它崩潰，你在LogCat中得到什麼信息？* – immibis 2015-04-01 23:25:24
@immibis它並不真正崩潰，它不會啓動，它只是說有問題，它不會啓動。順便說一句，我很感謝你試圖幫助我，我想要做的就是讓「MainActivity」成爲我的GUI，並且讓「Something」處理聽衆，讓他們都聚合成一個活動，但似乎不可能。 – user4601488 2015-04-01 23:38:45
Something.java的第32行是什麼？ – immibis 2015-04-02 00:59:51