在整個開發環境終於搞定 且也再次回想起之前寫 Java 相關的記憶
所以剛剛利用時間寫個簡單的計算機 讓自己回憶起更多這方面的 programming knowledge
這個 Calculator 有用到的部份主要有幾個:
1. 整個 AP 的畫面 Layout 不是透過 xml , 而是透過 Java code 一步步將之建立排版
此 Calculator 主要用到的是 LinearLayout, 共用了 7 個 LinearLayout 兜成的
每個 Layout 上放置不同的 widgets, 有 button, 有 EditText
2. Calculator 因為要去接收 key event, 所以實作了 OnClickListener Interface
在 class 裡實作 public void onClick(View v){} (和 Thread & Run function 一樣)
而在 onClick 裡面判定哪個 widget 被點選則是利用每個 widget 的 id
這個 id 是在一開始創造 button widget 時都會給一個值來作區別
-------------------------------- 以下則是此 Java source -----------------------------------------
package com.example.calculator;
import android.app.Activity;
import android.os.Bundle;
import android.content.Context;
import android.view.Gravity;
import android.view.ViewGroup;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.Button;
import android.graphics.Color;
import android.view.View;
import android.view.View.OnClickListener;
import android.util.Log;
public class Calculator extends Activity implements OnClickListener
{
private LinearLayout root;
private EditText resultVal;
private int val_1 = 0,val_2 = 0;
private int op = 0;
private static final int BT_0 = 0;
private static final int BT_1 = 1;
private static final int BT_2 = 2;
private static final int BT_3 = 3;
private static final int BT_4 = 4;
private static final int BT_5 = 5;
private static final int BT_6 = 6;
private static final int BT_7 = 7;
private static final int BT_8 = 8;
private static final int BT_9 = 9;
private static final int BT_CLEAR = 10;
private static final int BT_NAG = 11;
private static final int BT_DIV = 12;
private static final int BT_ADD = 13;
private static final int BT_SUB = 14;
private static final int BT_X = 15;
private static final int BT_EQUAL = 16;
private static final int BT_DOT = 17;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
//create root layout's params
LinearLayout.LayoutParams rootContainer = new LinearLayout.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT,
0.0f);
//create widget layout's params
LinearLayout.LayoutParams widgetContainer = new LinearLayout.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT,
ViewGroup.LayoutParams.FILL_PARENT,
1.0f);
root = new LinearLayout(this);
root.setOrientation(LinearLayout.VERTICAL);
root.setBackgroundColor(Color.LTGRAY);
root.setLayoutParams(rootContainer);
//the value field's layout on the top of screen
LinearLayout l1 = new LinearLayout(this);
l1.setOrientation(LinearLayout.HORIZONTAL);
l1.setBackgroundColor(Color.GRAY);
l1.setLayoutParams(widgetContainer);
root.addView(l1);
//the value field on the top of screen
resultVal = new EditText(this);
resultVal.setFocusable(false);
resultVal.setLayoutParams(widgetContainer);
resultVal.setText("0");
resultVal.setGravity(Gravity.CENTER_VERTICAL|Gravity.RIGHT);
l1.addView(resultVal);
//create 4 button of line 1
l1 = new LinearLayout(this);
l1.setOrientation(LinearLayout.HORIZONTAL);
l1.setBackgroundColor(Color.GRAY);
l1.setLayoutParams(widgetContainer);
root.addView(l1);
createButton(l1,widgetContainer,"c",BT_CLEAR);
createButton(l1,widgetContainer,"+/-",BT_NAG);
createButton(l1,widgetContainer,"/",BT_DIV);
createButton(l1,widgetContainer,"x",BT_X);
//create 4 button of line 2
l1 = new LinearLayout(this);
l1.setOrientation(LinearLayout.HORIZONTAL);
l1.setBackgroundColor(Color.GRAY);
l1.setLayoutParams(widgetContainer);
root.addView(l1);
createButton(l1,widgetContainer,"7",BT_7);
createButton(l1,widgetContainer,"8",BT_8);
createButton(l1,widgetContainer,"9",BT_9);
createButton(l1,widgetContainer,"-",BT_SUB);
//create 4 button of line 2
l1 = new LinearLayout(this);
l1.setOrientation(LinearLayout.HORIZONTAL);
l1.setBackgroundColor(Color.GRAY);
l1.setLayoutParams(widgetContainer);
root.addView(l1);
createButton(l1,widgetContainer,"4",BT_4);
createButton(l1,widgetContainer,"5",BT_5);
createButton(l1,widgetContainer,"6",BT_6);
createButton(l1,widgetContainer,"+",BT_ADD);
//create 4 button of line 3
l1 = new LinearLayout(this);
l1.setOrientation(LinearLayout.HORIZONTAL);
l1.setBackgroundColor(Color.GRAY);
l1.setLayoutParams(widgetContainer);
root.addView(l1);
createButton(l1,widgetContainer,"1",BT_1);
createButton(l1,widgetContainer,"2",BT_2);
createButton(l1,widgetContainer,"3",BT_3);
createButton(l1,widgetContainer,".",BT_DOT);
//create 4 button of line 4
l1 = new LinearLayout(this);
l1.setOrientation(LinearLayout.HORIZONTAL);
l1.setBackgroundColor(Color.GRAY);
l1.setLayoutParams(widgetContainer);
root.addView(l1);
createButton(l1,widgetContainer,"0",BT_0);
createButton(l1,widgetContainer,"=",BT_EQUAL);
setContentView(root);
}
private void createButton(LinearLayout layer,LinearLayout.LayoutParams widgetContainer,String str,int Id){
Button b = new Button(this);
b.setId(Id);
b.setText(str);
b.setTextColor(Color.RED);
b.setLayoutParams(widgetContainer);
b.setOnClickListener(this);
layer.addView(b);
}
public void onClick(View v){
Log.d("DEBUG", "v.getId() : "+v.getId());
switch (v.getId())
{
case BT_CLEAR:
val_1 = 0;
val_2 = 0;
resultVal.setText("0");
break;
case BT_0:
case BT_1:
case BT_2:
case BT_3:
case BT_4:
case BT_5:
case BT_6:
case BT_7:
case BT_8:
case BT_9:
val_1 = val_1 * 10 + v.getId();
resultVal.setText(Integer.toString(val_1));
break;
case BT_EQUAL:
case BT_ADD:
case BT_SUB:
case BT_DIV:
case BT_X:
switch (op)
{
case BT_ADD:
if (val_2 != 0)
val_2 = val_1 + val_2;
else
val_2 = val_1;
break;
case BT_SUB:
if (val_2 != 0)
val_2 = val_2 - val_1;
else
val_2 = val_1;
break;
case BT_DIV:
if (val_2 != 0 && val_1 > 0)
val_2 = val_2 / val_1;
else
val_2 = val_1;
break;
case BT_X:
if (val_2 != 0)
val_2 = val_2 * val_1;
else
val_2 = val_1;
break;
default:
val_2 = val_1;
break;
}
val_1 = 0;
resultVal.setText(Integer.toString(val_2));
if (v.getId() == BT_EQUAL)
{
val_1 = val_2;
op = 0;
val_2 = 0;
}
else
op = v.getId();
break;
}
}
}
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