[英]How can I access a function in another class?
我正在为Android开发一个必须访问另一个类的应用程序,但是我不知道为什么它不起作用。
在android 2.3.3中运行该应用程序时,它会强制关闭,我不明白为什么。 我认为该方法是正确的。
登录强制关闭手机android:
> app_vercode:1
device_model:u8800
build_version:111180
condition:1
processName:beta.tester
pid:13277
uid:10088
tag:null
shortMsg:java.lang.NullPointerException
longMsg:java.lang.NullPointerException: Unable to start activity ComponentInfo{beta.tester/beta.tester.BetaTesterActivity}: java.lang.NullPointerException
stackTrace:java.lang.RuntimeException: Unable to start activity ComponentInfo{beta.tester/beta.tester.BetaTesterActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1664)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1680)
at android.app.ActivityThread.access$1500(ActivityThread.java:117)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:130)
at android.app.ActivityThread.main(ActivityThread.java:3703)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at beta.tester.BetaTesterActivity.onCreate(BetaTesterActivity.java:23)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1628)
... 11 more
Detail logs:
编辑:此代码已经正确。
编码:
类BetaTesterActivity:
package beta.tester;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
public class BetaTesterActivity extends Activity {
public TextView text1;
private teste cmd;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
text1 = (TextView) findViewById(R.id.text1);
//Start the function
cmd = new teste();
cmd.start(this);
}
}
类睾丸:
package beta.tester;
public class teste {
//Function that I will start
public void start(BetaTesterActivity zav){
zav.text1.setText("Hello");
}
//
}
在teste
类中,您将创建一个无用的新BetaTesterActivity
。 您需要使用框架创建的实例。 将您的班级teste
更改为此:
public class teste {
//Function that I will start
public void start(BetaTesterActivity zav){
zav.text1.setText("Hello");
}
}
然后,在活动类的onCreate
方法中,您需要初始化cmd
,然后像这样调用start:
cmd.start(this);
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