【Android】——比較兩個版本的大小

首先是獲取到已安裝的版本的版本號，例如1.2.3a。其次是獲取最新版本的版本號，例如1.2.4b。

以下代碼爲了簡潔，直接進行版本比較思路書寫：

首先是佈局文件，兩個輸入框輸入的是版本號，一般版本號的格式是xxx.xxx.xx，一個按鈕用來觸發比較行爲，另一個TextView用來顯示比較結果。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="20dp"
    tools:context="com.example.administrator.comparestringapplication.MainActivity">

    <EditText
        android:id="@+id/string1"
        android:textAlignment="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="1.2.4b" />
    <EditText
        android:id="@+id/string2"
        android:textAlignment="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="1.2.3a" />
    <Button
        android:id="@+id/compare"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="比較"/>
    <TextView
        android:id="@+id/result"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

接下來是主要邏輯的代碼部分：

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    private EditText string1;
    private EditText string2;
    private Button compare;
    private TextView result;

    private String mString1;
    private String mString2;
    private String mResult;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView(savedInstanceState);
    }

    private void initView(Bundle savedInstanceState) {
        string1 = (EditText) findViewById(R.id.string1);
        string2 = (EditText)findViewById(R.id.string2);
        compare = (Button) findViewById(R.id.compare);
        result = (TextView) findViewById(R.id.result);
        compare.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                getData();
                compare2String();
                result.setText(mResult);
            }
        });
    }

    private void compare2String() {
       
        mResult = mString1 + "版本比" + mString2 + "版本";
        String[] strings11 = mString1.split("\\.");
        String[] strings21 = mString2.split("\\.");
        int x = strings11.length - strings21.length;
       if (x > 0){
           for(int i =0;i < x; i ++){
               mString2 += ".0";
           }
       }
       if(x < 0){
           x = -x;
           for(int i =0;i < x; i ++){
               mString1 += ".0";
           }
       }
        String[] strings1 = mString1.split("\\.");
        String[] strings2 = mString2.split("\\.");
        int index ;
        if(strings1.length <=strings2.length) {
            index = strings1.length;
        }else{
            index = strings2.length;
        }
        boolean a = false;
        boolean b = false;
        for (int j = 0; j < index; j++) {
            char[] s1 = strings1[j].toCharArray();
            char[] s2 = strings2[j].toCharArray();
            if (s1.length > s2.length) {
                mResult = mResult + "大";
                break;
            } else if (s1.length < s2.length) {
                mResult = mResult + "小";
                break;
            } else {
                for (int i = 0; i < s1.length; i++) {
                    if (s1[i] - s2[i] == 0) {
                        continue;
                    } else if (s1[i] - s2[i] > 0) {
                        a = true;
                        break;
                    } else {
                        b = true;
                        break;
                    }
                }
            }
            if(a){
                mResult = mResult + "大";
                break;
            }
            if (b){
                mResult = mResult + "小";
                break;
            }
            if (a == false && b == false){
                continue;
            }
        }
    }

    private void getData() {
        mString1 = string1.getText().toString().trim().toLowerCase();
        mString2 = string2.getText().toString().trim().toLowerCase();
    }
}

得到的結果如下：