Android开发初体验-CriminalIntent

Posted 2020-10-10

这次我们继续完善Criminal Intent应用，使其功能更加完善。

首先我们为Criminal Intent添加对话框，对话框既能引起用户的注意也可以接收用户的输入。在提示重要信息或提供用户选择方面，都非常有用。

1：创建DialogFragment,并给AlterDialog添加DatePicker

@Override

public Dialog onCreateDialog(Bundle savedInstanceState) {

View v = LayoutInflater.from(getActivity())
        .inflate(R.layout.dialog_date, null);

return new AlertDialog.Builder(getActivity())

        .setView(v)
        .setTitle(R.string.date_picker_title)
        .setPositiveButton(android.R.string.ok,null)   
        .create();

2：显示DialogFragment　　

private static final String DIALOG_DATE = "DialogDate";

mDateButton.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View v) {
        FragmentManager manager = getFragmentManager();
        DatePickerFragment dialog = DatePickerFragment
                .newInstance(mCrime.getDate());
        dialog.setTargetFragment(CrimeFragment.this, REQUEST_DATE);
        dialog.show(manager, DIALOG_DATE);
    }
});

3：响应DatePicker对话框

public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (resultCode != Activity.RESULT_OK) {
        return;
    }

    if (requestCode == REQUEST_DATE) {
        Date date = (Date) data
                .getSerializableExtra(DatePickerFragment.EXTRA_DATE);
        mCrime.setDate(date);
        updateCrime();
        updateDate();
    }

其次是工具栏设计。工具栏可放置菜单选项、提供应用导航、还能帮助统一设计风格、塑造品牌形象。

1：响应菜单选项

需在CrimeListFragment中

实现onOptionsItemSelected(MenuItem)方法    

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case R.id.new_crime:
            Crime crime = new Crime();
            CrimeLab.get(getActivity()).addCrime(crime);
            updateUI();
            mCallbacks.onCrimeSelected(crime);
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

在CrimeListFragment中

响应SHOWSUBTITLE菜单项单击事件

case R.id.show_subtitle:
    mSubtitleVisible = !mSubtitleVisible;
    getActivity().invalidateOptionsMenu();
    updateSubtitle();
    return true;

最后创建数据库

1：创建舒适数据库

创建CrimeBaseHelper类

public class CrimeBaseHelper extends SQLiteOpenHelper {
    private static final int VERSION = 1;
    private static final String DATABASE_NAME = "crimeBase.db";
    public CrimeBaseHelper(Context context) {
        super(context, DATABASE_NAME, null, VERSION);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    }
}

2：写入数据库

 使用ContentValues

private static ContentValues getContentValues(Crime crime) { 
   ContentValues values = new ContentValues(); 
   values.put(CrimeTable.Cols.UUID, crime.getId().toString()); 
   values.put(CrimeTable.Cols.TITLE, crime.getTitle()); 
   values.put(CrimeTable.Cols.DATE, crime.getDate().getTime()); 
   values.put(CrimeTable.Cols.SOLVED, crime.isSolved() ? 1 : 0); 
   return values; }

3：读取数据库    

调用query(...)方法查询记录

private CrimeCursorWrapper queryCrimes(String whereClause, String[] whereArgs) {
    Cursor cursor = mDatabase.query(
            CrimeTable.NAME,
            null, // Columns - null selects all columns
            whereClause,
            whereArgs,
            null, // groupBy
            null, // having
            null  // orderBy
    );
    return new CrimeCursorWrapper(cursor);
}