我对用户输入的EditText场。用户可以在按钮上输入值高达十位数number.when点击，我需要显示双precision这个数字的日志[数学日志]值。

我下面showned。结果如果我输入XXXXXXXXXX [考虑以此为号]结果输出必须看起来像这样yy.yy。

 包com.example.logvalue;进口android.os.Bundle;进口android.app.Activity;进口android.view.View;进口android.view.View.OnClickListener;进口android.widget.Button;进口android.widget.EditText;进口android.widget.Toast;公共类主要活动扩展{    @覆盖    保护无效的onCreate（捆绑savedInstanceState）{        super.onCreate（savedInstanceState）;        的setContentView（R.layout.main）;      编辑的EditText =（EditText上）findViewById（R.id.editText1）;      最终诠释野应=的Integer.parseInt（edit.getText（）的toString（））;       按钮B1 =（按钮）findViewById（R.id.button1）;        b1.setOnClickListener（新OnClickListener（）{            公共无效的onClick（查看为arg0）{        Toast.makeText（Main.this，的String.format（％2F，Math.log10（野应）），Toast.LENGTH_LONG）.show（）;            }        }）;    }} 

解决方案

使用的String.format（％2F，Math.log10（编号））语法。String类具有这种格式的功能正是这些。

我假设你想用的10个碱基对数。

说明：的String.format 是从C传统的的printf 的Java的equavalient ++。在％符号是指有一些东西被从参数列表中获取，点意味着我们要指定的小数位数，因此我们把2点后。希望我帮助。

I have a edittext field for users input. user can enter values up to ten digit number.when clicking on the button, i need to show the log [ mathematics log ] value of that number in double precision.

That i showned below. If i input xxxxxxxxxx [ consider this as number ] The output must look like this yy.yy.

package com.example.logvalue;
import android.os.Bundle;
import android.app.Activity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class Main extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
      EditText edit = (EditText) findViewById(R.id.editText1);
      final int noo = Integer.parseInt(edit.getText().toString());
       Button b1 = (Button) findViewById(R.id.button1);
        b1.setOnClickListener(new OnClickListener() {
            public void onClick(View arg0) {
        Toast.makeText(Main.this, String.format("%.2f", Math.log10(noo)) , Toast.LENGTH_LONG).show();
            }
        });



    }


}

Use the String.format("%.2f", Math.log10(number)) syntax. The String class has this format function exactly for these.

I assume you want logarithm with base of 10.

Explanation: String.format is the Java-equavalient of the traditional printf from C++. The % symbol means there is something to be fetched from the argument list, the point means that we want to specify the number of decimals, and hence we put a 2 after that point. Hope I helped.