Question

我在“设置”菜单中创建了一个允许用户输入其名称的设置。我现在需要知道的是如何显示该名称。除了在nameLabel右侧显示名称外，我几乎完成了所有工作。非常感谢任何帮助。

activity_main.xml中

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="10dp" >

<!-- The bill amount -->

<TextView
    android:id="@+id/billAmountLabel"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:padding="10dp"
    android:text="@string/bill_amount_label"
    android:textSize="20sp"
    android:textStyle="bold" />

<EditText
    android:id="@+id/billAmountEditText"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/billAmountLabel"
    android:layout_marginLeft="5dp"
    android:layout_toRightOf="@+id/billAmountLabel"
    android:ems="8"
    android:inputType="numberDecimal"
    android:text="@string/bill_amount"
    android:textSize="20sp" >

    <requestFocus />
</EditText>

<!-- The tip percent -->

<TextView
    android:id="@+id/percentLabel"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/billAmountLabel"
    android:layout_below="@+id/billAmountLabel"
    android:padding="10dp"
    android:text="@string/tip_percent_label"
    android:textSize="20sp"
    android:textStyle="bold" />

<TextView
    android:id="@+id/percentTextView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/percentLabel"
    android:layout_alignLeft="@+id/billAmountEditText"
    android:padding="5dp"
    android:text="@string/tip_percent"
    android:textSize="20sp" />

<Button
    android:id="@+id/percentDownButton"
    android:layout_width="45dp"
    android:layout_height="45dp"
    android:layout_alignBaseline="@+id/percentTextView"
    android:layout_marginLeft="25dp"
    android:layout_toRightOf="@+id/percentTextView"
    android:text="@string/decrease"
    android:textSize="20sp" />

<Button
    android:id="@+id/percentUpButton"
    android:layout_width="45dp"
    android:layout_height="45dp"
    android:layout_alignBaseline="@+id/percentDownButton"
    android:layout_toRightOf="@+id/percentDownButton"
    android:text="@string/increase"
    android:textSize="20sp" />

<!-- the tip amount -->

<TextView
    android:id="@+id/tipLabel"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/percentLabel"
    android:layout_below="@+id/percentLabel"
    android:padding="10dp"
    android:text="@string/tip_amount_label"
    android:textSize="20sp"
    android:textStyle="bold" />

<TextView
    android:id="@+id/tipTextView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/tipLabel"
    android:layout_alignLeft="@id/billAmountEditText"
    android:padding="5dp"
    android:text="@string/tip_amount"
    android:textSize="20sp" />

<!-- the total -->

<TextView
    android:id="@+id/totalLabel"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/tipLabel"
    android:layout_below="@+id/tipLabel"
    android:padding="10dp"
    android:text="@string/total_amount_label"
    android:textSize="20sp"
    android:textStyle="bold" />

<TextView
    android:id="@+id/totalTextView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/totalLabel"
    android:layout_alignLeft="@+id/tipTextView"
    android:padding="5dp"
    android:text="@string/total_amount"
    android:textSize="20sp" />

<TextView
    android:id="@+id/nameLabel"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_below="@+id/totalLabel"
    android:padding="10dp"
    android:text="Name"
    android:textSize="20sp"
    android:textStyle="bold" />
<TextView
    android:id="@+id/nameTextView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/nameLabel"
    android:layout_alignLeft="@+id/nameLabel"
    android:padding="5dp"
    android:text=""
    android:textSize="20sp" />

的preferences.xml

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen 
xmlns:android="http://schemas.android.com/apk/res/android">
<CheckBoxPreference
    android:key="pref_remember_percent"
    android:title="@string/remember_percent_title"
    android:summary="@string/remember_percent_summary"
    android:defaultValue="true" />
<ListPreference
    android:key="pref_rounding"
    android:title="@string/rounding_title"
    android:summary="@string/rounding_summary"
    android:dialogTitle="@string/rounding_title"
    android:entries="@array/rounding_keys"
    android:entryValues="@array/rounding_values"
    android:defaultValue="@string/rounding_default" />
<EditTextPreference
    android:defaultValue="Default value"
    android:key="pref_name"
    android:selectAllOnFocus="true"
    android:singleLine="true"
    android:text="Enter Name"
    android:title="Name" />
</PreferenceScreen>

MainActivity.java

import java.text.NumberFormat;

import android.os.Bundle;
import android.preference.PreferenceManager;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.inputmethod.EditorInfo;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.TextView.OnEditorActionListener;
import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;

public class TipCalculatorActivity extends Activity 
implements OnEditorActionListener, OnClickListener {

// define variables for the widgets
private EditText billAmountEditText;
private TextView percentTextView;   
private Button   percentUpButton;
private Button   percentDownButton;
private TextView tipTextView;
private TextView totalTextView;
private TextView nameTextView;
private TextView username;

// define instance variables that should be saved
private String billAmountString = "";
private float tipPercent = .15f;
private String nameLabel;

// define rounding constants
private final int ROUND_NONE = 0;
private final int ROUND_TIP = 1;
private final int ROUND_TOTAL = 2;

// set up preferences
private SharedPreferences prefs;
private boolean rememberTipPercent = true;
private int rounding = ROUND_NONE;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_tip_calculator);

    // get references to the widgets
    billAmountEditText = (EditText) findViewById(R.id.billAmountEditText);
    percentTextView = (TextView) findViewById(R.id.percentTextView);
    percentUpButton = (Button) findViewById(R.id.percentUpButton);
    percentDownButton = (Button) findViewById(R.id.percentDownButton);
    tipTextView = (TextView) findViewById(R.id.tipTextView);
    totalTextView = (TextView) findViewById(R.id.totalTextView);
    nameTextView = (TextView) findViewById(R.id.nameTextView);

    // set the listeners
    billAmountEditText.setOnEditorActionListener(this);
    percentUpButton.setOnClickListener(this);
    percentDownButton.setOnClickListener(this);

    // set the default values for the preferences
    PreferenceManager.setDefaultValues(this, R.xml.preferences, false);

    // get default SharedPreferences object
    prefs = PreferenceManager.getDefaultSharedPreferences(this);
    String username = 
PreferenceManager.getDefaultSharedPreferences(this).getString("pref_name", 
"No name");
nameTextView.setText(username);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_tip_calculator, menu);
    return true;
}

@Override
public void onPause() {
    // save the instance variables       
    Editor editor = prefs.edit();        
    editor.putString("billAmountString", billAmountString);
    editor.putFloat("tipPercent", tipPercent);
    editor.commit();        

    super.onPause();      
}

@Override
public void onResume() {
    super.onResume();

    // get preferences
    rememberTipPercent = prefs.getBoolean("pref_remember_percent", true);
    rounding = Integer.parseInt(prefs.getString("pref_rounding", "0"));

    // get the instance variables
    billAmountString = prefs.getString("billAmountString", "");
    if (rememberTipPercent) {
        tipPercent = prefs.getFloat("tipPercent", 0.15f);
    } else {
        tipPercent = 0.15f;
    }

    // set the bill amount on its widget
    billAmountEditText.setText(billAmountString);

    // calculate and display
    calculateAndDisplay();
}

public void calculateAndDisplay() {        
    // get the bill amount
    billAmountString = billAmountEditText.getText().toString();
    float billAmount; 
    if (billAmountString.equals("")) {
        billAmount = 0;
    }
    else {
        billAmount = Float.parseFloat(billAmountString);
    }

    // calculate tip and total
    float tipAmount = 0;
    float totalAmount = 0;
    float tipPercentToDisplay = 0;
    if (rounding == ROUND_NONE) {
        tipAmount = billAmount * tipPercent;
        totalAmount = billAmount + tipAmount;
        tipPercentToDisplay = tipPercent;
    }
    else if (rounding == ROUND_TIP) {
        tipAmount = StrictMath.round(billAmount * tipPercent);
        totalAmount = billAmount + tipAmount;
        tipPercentToDisplay = tipAmount / billAmount;
    }
    else if (rounding == ROUND_TOTAL) {
        float tipNotRounded = billAmount * tipPercent;
        totalAmount = StrictMath.round(billAmount + tipNotRounded);
        tipAmount = totalAmount - billAmount;
        tipPercentToDisplay = tipAmount / billAmount;
    }

    // display the other results with formatting
    NumberFormat currency = NumberFormat.getCurrencyInstance();
    tipTextView.setText(currency.format(tipAmount));
    totalTextView.setText(currency.format(totalAmount));

    NumberFormat percent = NumberFormat.getPercentInstance();
    percentTextView.setText(percent.format(tipPercentToDisplay));
}

@Override
public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
    int keyCode = -1; 
    if (event != null) {
       keyCode = event.getKeyCode();
    }
    if (actionId == EditorInfo.IME_ACTION_DONE ||
        actionId == EditorInfo.IME_ACTION_UNSPECIFIED ||
        keyCode == KeyEvent.KEYCODE_DPAD_CENTER || 
        keyCode == KeyEvent.KEYCODE_ENTER) {
        calculateAndDisplay();
    }        
    return false;
}

@Override
public void onClick(View v) {
    switch (v.getId()) {
    case R.id.percentDownButton:
        tipPercent = tipPercent - .01f;
        calculateAndDisplay();
        break;
    case R.id.percentUpButton:
        tipPercent = tipPercent + .01f;
        calculateAndDisplay();
        break;
    }
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case R.id.menu_settings:
            // Toast.makeText(this, "Settings", Toast.LENGTH_SHORT).show();
            startActivity(new Intent(getApplicationContext(), 
SettingsActivity.class));
            return true;
        case R.id.menu_about:
            // Toast.makeText(this, "About", Toast.LENGTH_SHORT).show();
            startActivity(new Intent(getApplicationContext(), 
AboutActivity.class));
            return true;

        default:
            return super.onOptionsItemSelected(item);
    }
}

}

Answer 1

您可以从EditTextPreference元素中读取名称的值，如下所示

String username = PreferenceManager.getDefaultSharedPreferences(this).getString("pref_name", "No name");

然后将其显示在TextView这样的

中

nameTextView.setText(username);

Answer 2

当用户更改UI中的值时，您的Preference会将其值保存在应用的默认SharedPreference对象中。您可以使用SharedPreference从任意位置访问默认PreferenceManager。例如，在MainActivity onCreate()：

中

SharedPreferences sharedPreferences =
                    PreferenceManager.getDefaultSharedPreferences(this);

为避免经常检查新值，请注册在首选项更改时（例如，由用户）通知的处理程序。在此示例中，活动将自身设置为处理程序：

sharedPreference.registerOnSharedPreferenceChangeListener(this);

因此，您的活动必须实现此界面：

public class MainActivity extends AppCompatActivity
    implements SharedPreferences.OnSharedPreferenceChangeListener {

最后，您实施onSharedPreferenceChanged：

@Override
public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
    String username = sharedPreferences.getString("pref_name", "default");
    textView_username.setText(username);
}

"pref_name"是您在preferences.xml中声明的首选项。

在对设置更改感兴趣的所有活动可能看起来像这样：

public class MainActivity extends AppCompatActivity
    implements SharedPreferences.OnSharedPreferenceChangeListener {

    TextView textView_username;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        textView_username = findViewById(R.id.textView_username);
        SharedPreferences sharedPreferences =
            PreferenceManager.getDefaultSharedPreferences(this);
        sharedPreference.registerOnSharedPreferenceChangeListener(this);
    }

    @Override
    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
        String username = sharedPreferences.getString("key", "default value");
        textView_username.setText(username);
    }
}

从应用程序中的EditTextPreference显示文本？

2 个答案: