Java 从另一个类修改自定义视图
我已在MyView类中创建了一个自定义视图,并希望在我的MainActivity类中使用Java 从另一个类修改自定义视图,java,android,xml,Java,Android,Xml,我已在MyView类中创建了一个自定义视图,并希望在我的MainActivity类中使用onSharedPreferenceChanged方法显示或隐藏mLevel 下面是MyView.java: public class MyView extends LinearLayout { private final TextView mLevel; public StatusBarView(Context context) { this(context, null,
onSharedPreferenceChanged
方法显示或隐藏mLevel
下面是MyView.java
:
public class MyView extends LinearLayout {
private final TextView mLevel;
public StatusBarView(Context context) {
this(context, null, 0);
}
public StatusBarView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public StatusBarView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
setGravity(Gravity.CENTER_VERTICAL);
LayoutInflater.from(context).inflate(R.layout.my_level_view, this);
mLevel = (TextView) findViewById(R.id.levelTextView);
}
public void showLevel(boolean bShowLevel) {
if (bShowLevel) {
mLevel.setVisibility(View.VISIBLE);
mLevel.setText(mService.getLevel());
} else {
mLevel.setVisibility(View.GONE);
}
}
}
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Display the fragment as the main content.
getFragmentManager().beginTransaction().replace(android.R.id.content, new PrefsFragment()).commit();
}
public class PrefsFragment extends PreferenceFragment
implements SharedPreferences.OnSharedPreferenceChangeListener {
private TextView mLevel;
private LevelService mLevelService = new LevelService();
private MyView mMyView = new MyView(getBaseContext());
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Load the preferences from an XML resource
addPreferencesFromResource(R.xml.preferences);
mLevel = (TextView) findViewById(R.id.levelTextView);
}
@Override
public void onResume() {
super.onResume();
getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
}
@Override
public void onPause() {
super.onPause();
getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);
}
@Override
public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
if (key.equals("showLevel")) {
mMyView.showLevel(prefs.getBoolean("showLevel", false));
}
}
}
这里有MainActivity.java
:
public class MyView extends LinearLayout {
private final TextView mLevel;
public StatusBarView(Context context) {
this(context, null, 0);
}
public StatusBarView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public StatusBarView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
setGravity(Gravity.CENTER_VERTICAL);
LayoutInflater.from(context).inflate(R.layout.my_level_view, this);
mLevel = (TextView) findViewById(R.id.levelTextView);
}
public void showLevel(boolean bShowLevel) {
if (bShowLevel) {
mLevel.setVisibility(View.VISIBLE);
mLevel.setText(mService.getLevel());
} else {
mLevel.setVisibility(View.GONE);
}
}
}
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Display the fragment as the main content.
getFragmentManager().beginTransaction().replace(android.R.id.content, new PrefsFragment()).commit();
}
public class PrefsFragment extends PreferenceFragment
implements SharedPreferences.OnSharedPreferenceChangeListener {
private TextView mLevel;
private LevelService mLevelService = new LevelService();
private MyView mMyView = new MyView(getBaseContext());
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Load the preferences from an XML resource
addPreferencesFromResource(R.xml.preferences);
mLevel = (TextView) findViewById(R.id.levelTextView);
}
@Override
public void onResume() {
super.onResume();
getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
}
@Override
public void onPause() {
super.onPause();
getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);
}
@Override
public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
if (key.equals("showLevel")) {
mMyView.showLevel(prefs.getBoolean("showLevel", false));
}
}
}
但当我用showLevel
键点击复选框时,我的应用程序崩溃。在AndroidStudio中,我从这一行开始得到NullPointerException:mLevel.setVisibility(View.VISIBLE)代码>尝试从另一个类而不是MyView(在MyView中工作正常)修改视图时
非常感谢您的帮助
更新:我在MyView
中添加了一个showLevel()
方法,并尝试在服务中访问它。正在工作。将代码替换为
public class MainActivity extends AppCompatActivity implements SetVisibilityInterface{
private TextView mLevel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mLevel = (TextView) findViewById(R.id.levelTextView);
// Display the fragment as the main content.
getFragmentManager().beginTransaction().replace(android.R.id.content, new PrefsFragment(this)).commit();
}
@Override
public void setVisibilityInterfaceAndData(int visibility, String value) {
if(visibility==View.VISIBLE){
mLevel.setVisibility(View.VISIBLE);
mLevel.setText(value);
}else {
mLevel.setVisibility(View.GONE);
}
}
public class PrefsFragment extends PreferenceFragment
implements SharedPreferences.OnSharedPreferenceChangeListener {
private TextView mLevel;
private Context mContext;
private LevelService mLevelService = new LevelService();
private SetVisibilityInterface mySetVisibilityInterface;
public PrefsFragment(Context context) {
mContext = context;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Load the preferences from an XML resource
addPreferencesFromResource(R.xml.preferences);
}
@Override
public void onResume() {
super.onResume();
getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
}
@Override
public void onPause() {
super.onPause();
getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);
}
@Override
public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
if (key.equals("showLevel")) {
try {
mySetVisibilityInterface = (SetVisibilityInterface) mContext;
if (prefs.getBoolean("showLevel", false)) {
mySetVisibilityInterface.setVisibilityInterfaceAndData(View.VISIBLE, mService.getLevel());
} else {
mySetVisibilityInterface.setVisibilityInterfaceAndData(View.GONE, "");
}
} catch (ClassCastException e) {
throw new ClassCastException(mContext.toString()
+ " must implement SetVisibilityInterface");
}
}
}
}
}
对于回调,您需要接口
public interface SetVisibilityInterface {
public void setVisibilityInterfaceAndData(int visibility, String value);
}
如果对你有效,请告诉我
并标记为答案,以便对其他人有用…将您的代码替换为
public class MainActivity extends AppCompatActivity implements SetVisibilityInterface{
private TextView mLevel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mLevel = (TextView) findViewById(R.id.levelTextView);
// Display the fragment as the main content.
getFragmentManager().beginTransaction().replace(android.R.id.content, new PrefsFragment(this)).commit();
}
@Override
public void setVisibilityInterfaceAndData(int visibility, String value) {
if(visibility==View.VISIBLE){
mLevel.setVisibility(View.VISIBLE);
mLevel.setText(value);
}else {
mLevel.setVisibility(View.GONE);
}
}
public class PrefsFragment extends PreferenceFragment
implements SharedPreferences.OnSharedPreferenceChangeListener {
private TextView mLevel;
private Context mContext;
private LevelService mLevelService = new LevelService();
private SetVisibilityInterface mySetVisibilityInterface;
public PrefsFragment(Context context) {
mContext = context;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Load the preferences from an XML resource
addPreferencesFromResource(R.xml.preferences);
}
@Override
public void onResume() {
super.onResume();
getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
}
@Override
public void onPause() {
super.onPause();
getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);
}
@Override
public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
if (key.equals("showLevel")) {
try {
mySetVisibilityInterface = (SetVisibilityInterface) mContext;
if (prefs.getBoolean("showLevel", false)) {
mySetVisibilityInterface.setVisibilityInterfaceAndData(View.VISIBLE, mService.getLevel());
} else {
mySetVisibilityInterface.setVisibilityInterfaceAndData(View.GONE, "");
}
} catch (ClassCastException e) {
throw new ClassCastException(mContext.toString()
+ " must implement SetVisibilityInterface");
}
}
}
}
}
对于回调,您需要接口
public interface SetVisibilityInterface {
public void setVisibilityInterfaceAndData(int visibility, String value);
}
如果对你有效,请告诉我
并标记为答案,以便对其他人有用…片段的onCreateView()
方法中有什么?这是我在MainActivity
中的内容,没有onCreateView()
。无论如何,我不能在我的其他两个类中修改视图,不仅仅是在主类中。是否在activity\u main.xml
中声明了levelTextView
?否,它是在my\u level\u view.xml中声明的?片段的onCreateView()
方法中有什么?这是我在main activity
中声明的,没有onCreateView()
。无论如何,我不能在我的其他两个类中修改视图,不仅仅是在主类中。是否在activity\u main.xml
中声明了levelTextView
?否,它是在my\u level\u view.xml中声明的谢谢您的帮助,但我正在尝试从主活动类在自定义视图中修改/更新mLevel
,不要在片段内创建另一个mLevel
,顺便说一句,这是一个首选项屏幕。那么您不能更改可见性,您将得到一个异常,因为无法从其他类修改另一个类的视图。您必须调用该类的一个方法,然后在那里设置可见性。看起来,如果我在MyView.java
中创建一个方法,并从扩展服务的类运行它(在onStartCommand中),它将正确运行代码。但我需要它被更新,每次有一个在我的复选框的变化。可以使用服务的onStart命令添加我的PrefsFragment吗?谢谢你的帮助,但我正在尝试从MainActivity类在我的自定义视图中修改/更新mLevel
,而不是在片段内创建另一个mLevel
,顺便说一句,这是一个PreferenceScreen。那么你不能更改可见性,您将得到一个异常,因为无法从其他类修改来自其他类的视图。您必须调用该类的一个方法,然后在那里设置可见性。看起来,如果我在MyView.java
中创建一个方法,并从扩展服务的类运行它(在onStartCommand中),它将正确运行代码。但我需要它被更新,每次有一个在我的复选框的变化。是否可以使用服务的onStart命令添加我的PrefsFragment?