Henry 的筆記 (blog): Android Studio 筆記

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2015年10月31日星期六

Android Studio R 顯示紅色

當 R 顯示紅色如下時, 可按 Build -> Rebuild Project 解決

EditView txtWrite = (EditText) findViewById(R.id.editText);

2015年10月27日星期二

android 取得目前時間 System.currentTimeMillis()

取得目前時間可用 System.currentTimeMillis()

2015年10月25日星期日

android 讀取, 寫入及刪除檔案 (internal storage)

版面要加入一個editView, 一個textView及三個 Button (editView, textView, btnRead, btnWrite, btnDel)

MainActivity.java

import android.content.Context;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.view.View.OnClickListener;
import android.widget.Toast;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;


public class MainActivity extends ActionBarActivity {
    private Button btnTxtRead;
    private Button btnTxtWrite;
    private Button btnFileDel;
    private EditText txtWrite;
    private TextView txtRead;
    String fileName = "dateRec.dat";


    @Override

   protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        txtWrite = (EditText) findViewById(R.id.editText);
        txtRead = (TextView) findViewById(R.id.textView);

        btnTxtRead = (Button) findViewById(R.id.btnRead);
        btnTxtWrite = (Button) findViewById(R.id.btnWrite);
        btnFileDel = (Button) findViewById(R.id.btnDel);

        btnTxtRead.setOnClickListener(btnListener);
        btnTxtWrite.setOnClickListener(btnListener);
        btnFileDel.setOnClickListener(btnListener);


    }


    private void writer() {
        FileOutputStream fos = null;
        
        try {
            fos = openFileOutput(fileName, Context.MODE_PRIVATE);
            fos.write(txtWrite.getText().toString().getBytes());
            fos.close();

            File file = new File(getFilesDir() + "/" + fos);
            Toast.makeText(getApplicationContext(), file.getAbsolutePath(), Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    private void reader() {
        FileInputStream fos = null;
        BufferedInputStream buffered = null;
        txtRead.setText("");

        try {
            fos = openFileInput(fileName);
            buffered = new BufferedInputStream(fos);
            byte[] buffbyte = new byte[200];
            txtRead.setText("");
            do {
                int flag = buffered.read(buffbyte);
                if (flag == -1) {
                    break;
                } else {
                    txtRead.append(new String(buffbyte), 0, flag);
                }
            }while (true);
            buffered.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void fileDel() {
        File file = new File(getFilesDir() + "/" + fileName);
        if (file.exists()){
            file.delete();
            Toast.makeText(getBaseContext(),
                    "File deleted",
                    Toast.LENGTH_SHORT).show();
        }else{
            Toast.makeText(getBaseContext(),
                    "File doesn't exist",
                    Toast.LENGTH_SHORT).show();
        }
    }

    private OnClickListener btnListener = new OnClickListener() {
            public void onClick(View v) {
                switch (v.getId()) {
                    case R.id.btnRead:
                        try {
                            Toast.makeText(getApplicationContext(),
                                    "Read button pressed", Toast.LENGTH_SHORT).show();
                            reader();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        break;
                    case R.id.btnWrite:
                        try {
                            Toast.makeText(getApplicationContext(),
                                    "Write button pressed", Toast.LENGTH_SHORT).show();
                            writer();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        break;
                    case R.id.btnDel:
                        try {
                            Toast.makeText(getApplicationContext(),
                                    "Del button pressed", Toast.LENGTH_SHORT).show();
                            fileDel();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        break;
                }


            }


        };
    }

2015年10月23日星期五

android 有多個按鍵 (button) 時使用switch statement

版面要加入三個 Button (btnRead, btnWrite, btnDel)

MainActivity.java

import android.content.DialogInterface;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.view.View.OnClickListener;
import android.widget.Toast;


public class MainActivity extends ActionBarActivity {
    private Button btnTxtRead;
    private Button btnTxtWrite;
    private Button btnFileDel;

    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btnTxtRead = (Button) findViewById(R.id.btnRead);
        btnTxtWrite = (Button) findViewById(R.id.btnWrite);
        btnFileDel = (Button) findViewById(R.id.btnDel);

        btnTxtRead.setOnClickListener(btnListener);
        btnTxtWrite.setOnClickListener(btnListener);
        btnFileDel.setOnClickListener(btnListener);
    }

    private OnClickListener btnListener = new OnClickListener() {
            public void onClick(View v) {
                switch (v.getId()) {
                    case R.id.btnRead:
                        try {
                            Toast.makeText(getApplicationContext(), "Read button pressed", Toast.LENGTH_SHORT).show();

                        } catch (Exception e) {
                            e.printStackTrace();
                        }

                        break;

                   case R.id.btnWrite:
                        try {
                            Toast.makeText(getApplicationContext(), "Write button pressed", Toast.LENGTH_SHORT).show();

                        } catch (Exception e) {
                            e.printStackTrace();
                        }

                        break;

                case R.id.btnDel:
                        try {
                            Toast.makeText(getApplicationContext(), "Del button pressed", Toast.LENGTH_SHORT).show();

                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        break;
                }


            }


        };
    }

2015年10月13日星期二

預設中, 螢幕旋轉時會重新執行 onCreate(), 要制止重新執行, 可以有以下兩個方法:

1. 禁止螢幕旋轉
        於 AndroidManifest.xml 檔裡, 在 <activity> </activity> 中, 添加一條屬性資訊：

        android:screenOrientation="portrait"       （強制縱向）
        android:screenOrientation="landscape" （強制橫向）

        如下:

        <activity android:name=".SomeActivity"
          android:label="@string/app_name"
          android:screenOrientation="portrait">

2. 螢幕旋轉時不重新執行onCreate()
於 AndroidManifest.xml 檔裡, 在 <activity> </activity> 中, 添加一條屬性資訊：

android:configChanges=”orientation|keyboardHidden”

        (如API 等級等於或高於13要加 screenSize)
android:configChanges="orientation|keyboardHidden|screenSize”

        如下:

        <activity android:name=".SomeActivity"
          android:label="@string/app_name"
          android:configChanges="orientation|keyboardHidden|screenSize">

        於 activity 中, 加入

        @Override
         public void onConfigurationChanged(Configuration newConfig) {
   super.onConfigurationChanged(newConfig);
   if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
        }
      else {
        }
}

android 禁止螢幕旋轉 (強制設定為縱向或橫向)

於 AndroidManifest.xml 檔裡, 在 <activity> </activity> 中, 添加一條屬性資訊：

android:screenOrientation="portrait"       （強制縱向）
android:screenOrientation="landscape" （強制橫向）

如下:

<activity android:name=".SomeActivity"
    android:label="@string/app_name"
    android:screenOrientation="portrait">

android 寫入檔案 (簡短文字) FileInputStream, FileOutputStream

寫入簡短文字可使用寫入文字檔方法, 如複雜便要用SQLite

版面要加入一個editView, 一個textView 及兩個 Button (editView1, textView2, btnWrite, btnRead)

輸入字於 editView1, 按下 btnWrite 便會寫入檔案 output 及顯示檔案路徑 (toast), 按下 btnRead 便會讀出檔案及顯示於 textView2

注意: 讀取中文字, 中文字每個要 2 個 Byte.

MainActivity.java

import android.content.Context;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;

public class MainActivity extends ActionBarActivity {

    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final EditText txtWrite = (EditText) findViewById(R.id.editText1);
        final TextView txtRead = (TextView) findViewById(R.id.textView2);

        Button btnTxtRead = (Button) findViewById(R.id.btnRead);
        Button btnTxtWrite = (Button) findViewById(R.id.btnWrite);


        btnTxtWrite.setOnClickListener(new View.OnClickListener() {
            @Override            public void onClick(View arg0) {

                try {
                    FileOutputStream fos = openFileOutput("output", Context.MODE_PRIVATE);
                    fos.write(txtWrite.getText().toString().getBytes());
                    fos.close();

                    File file = new File(getFilesDir() + "/" + fos);
                    Toast.makeText(getApplicationContext(), file.getAbsolutePath(), Toast.LENGTH_SHORT).show();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });

        btnTxtRead.setOnClickListener(new View.OnClickListener() {
            @Override            public void onClick(View arg0) {

                FileInputStream fos = null;
                BufferedInputStream buffered = null;

                try {
                    fos = openFileInput("output");
                    buffered = new BufferedInputStream(fos);
                    byte[] buffbyte = new byte[200];
                    txtRead.setText("");
                    do {
                        int flag = buffered.read(buffbyte);
                        if (flag == -1) {
                            break;
                        } else {
                            txtRead.append(new String(buffbyte), 0, flag);
                        }
                    }while (true);
                    buffered.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }
}

2015年9月24日星期四

android 日期比較

版面要加入兩個 textView 及一個 Button (textView1, textView2, ChooseDateBtn)
此例以按選擇日子與現時日子作相減, 日子以微秒計算, 所以用 getTimeInMillis() 取得微秒後相減, 得出結果後再轉為秒, 分, 時, 日.

1000微秒 = 1秒

如要將時分秒設定為 0 用作計算, 可用 clear, 以下面為例, 現時日子可加入以下三句便可將時分秒設定為 0.

rightNow.clear(Calendar.HOUR);
rightNow.clear(Calendar.MINUTE);
rightNow.clear(Calendar.SECOND);

import android.app.DatePickerDialog;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.TextView;
import java.util.Calendar;
import java.util.GregorianCalendar;

public class MainActivity extends ActionBarActivity {

    Calendar rightNow = Calendar.getInstance();
    TextView DisplayDate1;
    TextView DisplayDate2;
    int cmonth, rmonth;


    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button changeDate = (Button) findViewById(R.id.ChooseDateBtn);
        DisplayDate1 = (TextView) findViewById(R.id.textView1);
        DisplayDate2 = (TextView) findViewById(R.id.textView2);

        changeDate.setOnClickListener(new View.OnClickListener() {

            @Override            public void onClick(View arg0) {

                new DatePickerDialog(MainActivity.this, d,
                        rightNow.get(Calendar.YEAR), rightNow.get(Calendar.MONTH),
                        rightNow.get(Calendar.DAY_OF_MONTH)).show();

            }
        });
    }

    DatePickerDialog.OnDateSetListener d = new DatePickerDialog.OnDateSetListener() {

        @Override        public void onDateSet(DatePicker view, int year, int monthOfYear,
                              int dayOfMonth) {


            cmonth = monthOfYear + 1;
            rmonth = rightNow.get(Calendar.MONTH) + 1;



            Calendar c = new GregorianCalendar(year, monthOfYear, dayOfMonth,
                    rightNow.get(Calendar.HOUR_OF_DAY), rightNow.get(Calendar.MINUTE),
                    rightNow.get(Calendar.SECOND));

            long diff = c.getTimeInMillis() - rightNow.getTimeInMillis();
            long diffSec = diff / 1000;
            long diffMins = diff / (60 * 1000);
            long diffHrs = diff / (60 * 60 * 1000);
            long diffDays = diff / (24 * 60 * 60 * 1000);


            DisplayDate1.setText("Choosen date is :" + dayOfMonth + "/" + cmonth + "/" + year +
                    "  Millisecond is :" + c.getTimeInMillis() + "\n" + "Current date is :" +
                    rightNow.get(Calendar.DAY_OF_MONTH) + "/" +
                    rmonth + "/" + rightNow.get(Calendar.YEAR) +
                    "  Millisecond is :" + rightNow.getTimeInMillis());
            DisplayDate2.setText("Date difference in seconds: " + diffSec +"\n"+
                    "Date difference in minutes: "+diffMins+"\n"+ "Date difference in hours: "+
                    diffHrs +"\n"+"Date difference in days: " + diffDays);



        }
    };
}

2015年8月26日星期三

android DatePickerDialog 彈出日期選擇

注意:

版面要加入一個 textView 及一個 Button (textView1, ChooseDateBtn)

import android.app.DatePickerDialog;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.TextView;

import java.util.Calendar;

public class MainActivity extends ActionBarActivity {

    Calendar c = Calendar.getInstance();
    TextView DisplayDate;
    int cday, cmonth, cyear;

    @Override

       protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button changeDate = (Button) findViewById(R.id.ChooseDateBtn);
        DisplayDate = (TextView) findViewById(R.id.textView1);

        changeDate.setOnClickListener(new OnClickListener() {

            @Override

             public void onClick(View arg0) {

                new DatePickerDialog(MainActivity.this, d,
                        c.get(Calendar.YEAR), c.get(Calendar.MONTH), c.get(Calendar.DAY_OF_MONTH)).show();

            }
        });
    }

    DatePickerDialog.OnDateSetListener d = new DatePickerDialog.OnDateSetListener() {

        @Override

            public void onDateSet(DatePicker view, int year, int monthOfYear,
                              int dayOfMonth) {

            cday = dayOfMonth;
            cmonth = monthOfYear + 1;
            cyear = year;

            DisplayDate.setText("Choosen date is :" + cday + "/" + cmonth + "/" + cyear);
        }
    };
}

2015年8月22日星期六

android DatePicker 日期選擇

以下是簡單日期選擇例子

注意:

版面要加入兩個 textView 及一個 DatePick (textView1, textView2, datePicker1)

因 Bug 關係, DatePick 放置後會顯示 Rendering Problems, 及不會顯示 DatePick, 但 run app 後會在 app 顯示

預設日期

datepick.init(2016,1,4,onDateChanged);

月份係由 0 至 11, 當顯示數字時要加 1, array 係由 0 開始, 所以不須要

Integer.toString(monthOfYear+1)

加入此兩個可改變日期選擇為轉動選擇

datepick.setCalendarViewShown(false);
datepick.setSpinnersShown(true);

import android.app.Activity;
import android.os.Bundle;
import android.widget.DatePicker;
import android.widget.TextView;


public class MainActivity extends Activity {
    @Override    protected void onCreate(Bundle savedInstanceState)  {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        DatePicker datepick = (DatePicker)
                findViewById(R.id.datePicker1);
        datepick.init(2016,1,4,onDateChanged);
        //    datepick.setCalendarViewShown(false);

        //    datepick.setSpinnersShown(true);    }

    DatePicker.OnDateChangedListener onDateChanged=
            new DatePicker.OnDateChangedListener() {
                @Override

              public void onDateChanged(
                        DatePicker view,
                        int year,
                        int monthOfYear,
                        int dayOfMonth) {
                    final String[] MMM = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
                    TextView tv1 = (TextView)findViewById(R.id.textView1);
                    TextView tv2 = (TextView)findViewById(R.id.textView2);
                    
                    tv1.setText(Integer.toString(dayOfMonth) +
                            "/"+Integer.toString(monthOfYear+1)+
                            "/"+Integer.toString(year) );

                    tv2.setText(Integer.toString(dayOfMonth) +
                            "/"+(MMM[monthOfYear])+
                            "/"+Integer.toString(year) );
                                    }
            };
}

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2015年10月31日 星期六

2015年10月27日 星期二

2015年10月25日 星期日

2015年10月23日 星期五

2015年10月13日 星期二

2015年9月24日 星期四

2015年8月26日 星期三

2015年8月22日 星期六