[英]I have created a small book program, I am new to java. Can't find what the error or mistake in this code?
[英]Mistake in this small Java program
這段代碼有什么錯誤? 當我運行該程序時,它說“應用程序buttonProj(進程com.example.buttonproj)已意外停止。請重試”。我只是嘗試創建一個“添加和減去”按鈕,用戶可以單擊它以增加或減少數字i 。
package com.example.buttonproj;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends Activity {
int counter;
Button add, sub;
TextView display;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
counter = 0;
add = (Button) findViewById(R.id.bAdd);
sub = (Button) findViewById(R.id.bSub);
display = (TextView) findViewById(R.id.textView1);
add.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
counter +=1;
display.setText(counter);
}
});
sub.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
counter--;
display.setText(counter);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
采用
display.setText(""+counter);
//OR
display.setText(String.valueOf(counter));
代替
display.setText(counter);
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